Impact of Climate Change on Transboundary Water Sharing

Stephen E. Draper1 and James E. Kundell2

Abstract: The issue of climate change has surfaced as a potential impediment to effective long-range policies and management of water
resources. The Intergovernmental Panel on Climate Change 共IPCC兲 recently published a report substantiating the argument that global
warming is occurring. The IPCC reported that while sustainable water yields may or may not be reduced in the long-term average, they
will almost certainly be less reliable in the short term. Climate change challenges existing water resources management practices by
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adding uncertainty. This will be an especially troubling issue for transboundary water sharing agreements. The risks imposed by climate
change to transboundary water sharing agreements are discussed and the agreements most at risk are identified by the region in which they
are located.
DOI: 10.1061/共ASCE兲0733-9496共2007兲133:5共405兲
CE Database subject headings: Climatic changes; Water resources; Water policy; Water supply.

Introduction The problem of water allocation within a single political juris-

diction is difficult enough because of the competing forces vying
The advancement of civilization as we know it requires adequate for water, but issues are usually resolved because a legal process
supplies of quality water on a regular and sustained basis. The 共laws and regulations兲 in which an allocation process is defined
demands for quality water are varied, each with a need for in- and a legal forum 共the courts兲 in which allocation disputes may be
creased quantities of what has become a scarce resource. The resolved. When the water to be allocated is shared by two or more
various demands for water are all essential to our way of life: political jurisdictions, however, the problem becomes more chal-
economic growth and prosperity, agriculture, and improved qual- lenging. In these cases, there is frequently no substantive legal
ity of life. These demands include sufficient quality water for process to guide the water allocation process and only tenuous
adequate public health and prosperity of humans as well as the forums in which to resolve disputes. Allocation normally occurs
aquatic ecosystem. Every level of the food chain, from bacteria through a consensus among the parties, usually in the form of
and algae to humans and other mammals, requires quality water transboundary water sharing agreement or compact.
on a regular and sustained basis.
The demands for adequate supplies of quality water continue
to grow at an accelerating pace while the supply of source water Transboundary Water Sharing
remains essentially constant, at least on a global basis. Water
scarcity, once confined to specific arid regions, has become the Sharing water across political boundaries is not an unusual phe-
norm. It is the ultimate goal of water management to allocate the nomenon. Basins shared by two or more governments cover
scarce supplies of water to maximize the return from each of the almost two-thirds of the global landmass. As noted in the Intro-
water user sectors. To reach this goal, those involved in the allo- duction, forty percent 共40%兲 of the world’s population depends on
cation process—lawmakers, policymakers, regulators, engineers, these shared river basins for the water they need. Over 90% of the
scientists, economists, and others—must be able to predict what population in the continental United States depends on waters
source water will be available in the future to allocate. Accurate shared with other states 共Draper 2002兲.
and reliable data and information on source water supplies are As with water allocation within a single legal jurisdiction, al-
key requirements in effective water planning and management location of shared waters is based on being able to accurately
共Dellapenna 1997; Draper 1997; Sophocleous 1998; Vörösmarty predict the quantity and quality of water that can be allocated in
2002兲. the future. A water sharing agreement usually focuses on alloca-
tion of water under conditions determined from the historical
1
Founder, the Stephen E. Draper Center and Archives for the Waters record. Thus, developing an effective agreement requires accurate
of Georgia in History, Law and Policy, Univ. of Georgia Library, 1401 and precise knowledge of past hydrological conditions. Other-
Peachtree St., NE, Suite 500, Atlanta, GA 30309. wise, the result may be significant disputes over the terms of an
2
Senior Associate and Hill Distinguished Fellow in the Carl Vinson agreement, significantly impairing the agreement’s usefulness for
Institute of Government and Professor of Environmental Policy in the the parties 共Berman and Wihbey 1999; The Ohio Valley Sanita-
Institute of Ecology at the Univ. of Georgia, Athens, GA 30602. tion Commission 2000兲.
Note. Discussion open until February 1, 2008. Separate discussions Predicting the future yield of shared water sources based on
must be submitted for individual papers. To extend the closing date by
the historical record can result, however, in significant future
one month, a written request must be filed with the ASCE Managing
Editor. The manuscript for this paper was submitted for review and pos- problems. The question of the reliability of past hydrologic
sible publication on May 1, 2007; approved on May 11, 2007. This paper records may be a significant problem. First, even what appear to
is part of the Journal of Water Resources Planning and Management, be long-duration records 共say the last 30 or 50 years兲 may not be
Vol. 133, No. 5, September 1, 2007. ©ASCE, ISSN 0733-9496/2007/5- representative of the cycles of hydrologic variation. Second, man-
405–415/$25.00. made changes in flow conditions 共from storage, diversions, and

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J. Water Resour. Plann. Manage. 2007.133:405-415.

 changes to impervious surfaces兲 may skew the reliability of his- ence Basis of the Fourth Assessment, are directly related to water
toric data 共Draper 2006兲. resources 共WGI 2007兲. Conclusions of the IPCC Reports raise
However, even if a detailed, accurate historical flow record of different levels of concern for different parts of the globe.
the shared water resource exists, there is a significant likelihood
that it will not accurately predict future yields. Climate change • Warming of the climate system is unequivocal, as is now
has surfaced as a potential impediment to effective long-range evident from observations of increases in global average air
policies and management of water resources 共Nicholls 2000兲. and ocean temperatures, widespread melting of snow and
There is now little argument that global warming is occurring ice, and rising global mean sea level.
共IPCC 2007; Jackson et al. 2001; National Academy of Sciences • At continental, regional, and ocean basin scales, numerous
2001; Bennett and Pendlebury 1998兲. Sustainable water yields long-term changes in climate have been observed. These
may or may not be reduced in the long-term average, but they will include changes in Arctic temperatures and ice, widespread
be almost certainly less reliable in the short term 共Sophocleous changes in precipitation amounts, ocean salinity, wind pat-
1998兲. A rapidly growing body of evidence suggests that we are terns, and aspects of extreme weather including droughts,
entering a somewhat warmer and definitely more variable world. heavy precipitation, heat waves, and the intensity of tropi-
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Climate change challenges existing water resources management cal cyclones.

practices by adding to the uncertainty of future source water • Anthropogenic forcing is likely to have contributed to
availability 共IPCC 2007; Vorosmarty 2002兲. changes in wind patterns, affecting extra-tropical storm
On April 6, 2007, the Intergovernmental Panel on Climate tracks and temperature patterns in both hemispheres. How-
Change published summaries of its fourth assessment that de- ever, the observed changes in the Northern Hemisphere cir-
tailed the expected effects of climate change. Among those ex- culation are larger than simulated in response to 20th cen-
pected effects, many to a high degree of certainty, were specific tury forcing change.
direct and indirect effects that will further complicate the quest • There is now higher confidence in projected patterns of
for adequate supplies of quality water that are needed to sustain warming and other regional-scale features, including
civilization as we know it. changes in wind patterns, precipitation, and some aspects of
extremes and of ice.
• Snow cover is projected to contract. Widespread increases
Intergovernmental Panel on Climate Change in thaw depth are projected over most permafrost regions.
• It is very likely that hot extremes, heat waves, and heavy
The scientific community has considered the issue of global cli- precipitation events will continue to become more frequent.
mate change from the perspective of various disciplines for many • Increases in the amount of precipitation are very likely in
years. During the mid-1970s, many leading climate scientists high latitudes, while decreases are likely in most subtropi-
were warning of the significant problems that might arise from cal land regions.
climate change, urging the government to take action to avert • Anthropogenic warming and sea level rise would continue
disaster 共Weart 2007兲. In 1988, in response to these scientific for centuries due to the timescales associated with climate
concerns, the World Meteorological Organization 共WMO兲 and the processes and feedbacks, even if greenhouse gas concentra-
United Nations Environment Programme 共UNEP兲 established the tions were to be stabilized.
Intergovernmental Panel on Climate Change 共IPCC兲. On April 6, 2007, the IPCC issued the second of three working
The mandate of the IPCC was limited to assessing “on a com- group reports, Working Group II Contribution to the Intergovern-
prehensive, objective, open, and transparent basis the scientific, mental Panel on Climate Change Fourth Assessment Report
technical, and socioeconomic information relevant to understand- Climate Change 2007: Climate Change Impacts, Adaptation and
ing the scientific basis of risk of human-induced climate change, Vulnerability, Summary for Policymakers 共WGII 2007兲. The key
its potential impacts, and options for adaptation and mitigation” impacts described in the report are shown in Fig. 1. Many of their
共IPCC 2007兲. general conclusions are directly or indirectly related to water
Because the final reports of the IPCC are invariably controver-
resources.
sial for a variety of reasons, it is important to recognize two of the
principles that govern the work of the IPCC. First, since the IPCC • The impacts of observed climate change include:
is an intergovernmental body, the final IPCC Assessment Report 1. Many natural systems on all continents and some
involves both peer review by experts and review by governments. oceans affected by regional climate change and rising
It is not solely a scientific appraisal of the evidence for climate temperatures; and
change. Second, decisions are normally made by consensus 2. Warming caused by human activities has likely had a
共IPCC 2007兲. discernible impact on the global level on many physi-
Although the reports are an amalgamation of science and poli- cal and biological systems.
tics 共national and international兲, they are science-based. Conse- • Specific systems and sectors are very vulnerable:
quently, the reports provide tentative conclusions based on the 1. Coral reefs and sea–ice regions;
available data and information. 2. Tundra, boreal forests, mountain, and Mediterranean
regions;
3. Low-lying coasts, mangroves, and salt marshes;
IPCC 2007 Assessment Report 4. Water resources in midlatitudes and dry Tropics;
5. Low-latitude agriculture; and
On February 6, 2007, the IPCC issued the first of three working 6. Human health where adaptive capacity is low.
group reports, which will provide the basis for the IPCC Fourth • Some regions will be more affected than others:
Assessment Report to be published in late 2007. Eight conclu- 1. Arctic;
sions of the Working Group I, responsible for the Physical Sci- 2. Sub-Saharan Africa;

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Fig. 1. 共Color兲 Key impacts 共WGII 2007b, with permission兲

3. Small islands; and • It is virtually certain there will be warmer and fewer cold
4. Asian megadeltas. days and nights; warmer/more frequent hot days and nights
• Impacts of extreme weather events are expected to over most land areas. This is expected to have effects on
increase: water resources relying on snow melt; and cause increased
• Adaptation will be necessary to address impacts resulting evapotranspiration rates.
from the warming which is already unavoidable due to past • It is very likely that the frequency of warm spells/heat
emissions; and waves will increase over most land areas. This effect is
• Vulnerability depends not only on climate change but also expected to increase water demand and aggravate water
on development paths; sustainable development can reduce quality problems, e.g., algal blooms.
vulnerability. • The increased frequency of heavy precipitation events over
most areas is very likely. This will have adverse effects on
The WGII Report presented more detailed impacts on water
the quality of surface and groundwater, causing contamina-
resources systems 共WGII 2007兲.
tion of water supply; water scarcity may be relieved.
1. Based on growing evidence, there is high confidence that the
• It is likely that the amount of area affected by drought will
following types of hydrological systems are being affected
increase, causing increased water stress.
around the world:
• It is likely that intense tropical cyclone activity increases,
• Increased run-off and earlier spring peak discharge in many
causing power outages and disruption of public water
glacier- and snow-fed rivers; and
supply.
• Warming of lakes and rivers in many regions, with effects
• Increased incidences of extreme high sea level will likely
on thermal structure and water quality.
increase, causing decreased freshwater availability due to
2. Confidence has increased that some weather events and ex-
saltwater intrusion.
tremes will become more frequent, more widespread, and/or
more intense during the 21st century; and more is known The apparent inconsistency between the prediction of in-
about the potential effects of such changes. 共WGII 2007兲: creased frequency of heavy precipitation events over most areas

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 and the prediction of an increase in the areas affected by drought
may be explained by separating individual precipitation events
from the total amount of precipitation experienced in a particular
area. For instance, historically an area may have received an av-
erage of 2.5 cm 共1.0 in.兲 of rain over four days each week during
a three-month period. This would total 30.5 cm 共12.0 in.兲 for the
three-month period. Under climate change conditions, the area
might receive 10 cm 共3.9 in.兲 of rain each week during the first
month and no rain during the other months. This region will re-
ceive more rain—a total of 40 cm 共15.8 in兲—yet may experience
water scarcity during the last tow months. The precipitation in-
tensity has increased but the total amount of precipitation has
decreased.
On May 4, 2007, the IPCC issued the third of three working
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group reports, “Working Group III Contribution to the Intergov-

ernmental Panel on Climate Change Fourth Assessment Report Fig. 2. Basins with water international sharing agreements 共Trans-
Climate Change 2007: Mitigation of Climate Change, Summary boundary freshwater dispute database: www.transboundarywaters.
for Policymakers” 共WGIII 2007兲. Two of their general conclu- orst.edu兲
sions are directly or indirectly related to water resources.
The Working Group III report observes that certain climate
change mitigation technologies and practices are currently com- Flood and drought cycles will probably increase in fre-
mercially available. Among these are hydropower as a renewable quency. Land-use change could exacerbate such events.
energy source and controlled waste water treatment to reduce 2. The prediction of warmer, more frequent hot days and nights
methane and N2O emissions. As a mitigation option in the over most land areas will intensify snow and permafrost melt
transportation sector, “model shifts from road to rail and inland and increase evapotranspiration. The increase in water de-
waterway shipping,” is suggested. The report also notes that mand due to warming will be significant in some areas and
“forest-related mitigation activities can considerably reduce water quality degradation may result from warming, e.g.,
共greenhouse gas兲 emissions” as well as benefiting watershed con- algae blooms.
servation and helping manage water runoff 共WGIII 2007兲. This conclusion corroborates the prediction that precipita-
Although the report presents no other mitigation efforts that tion will increase in some seasons and decrease in others
directly relate to water resources, several of the recommenda- 共Hahn and Palmer 2001兲. Because snowpack is very likely to
tions, if implemented, have an indirect significance on the man- decrease 共National Academy of Sciences 2001兲 and early
agement of water resource allocation. The most significant is the snow melt will likely happen due to higher temperatures,
mitigation report’s advocacy of sustainability. “Making develop- “peak streamflow will move from spring to winter in many
ment more sustainable by changing development paths can make areas where snowfall currently is an important component of
a major contribution to climate change mitigation . . .”; the report the water balance” 共IPCC 2007; National Academy of Sci-
emphasizes energy efficiency and renewable energy but cautions ences 2001兲. The greatest changes in regions like central and
against “displacement of local populations.” Reforestation and eastern Europe and the southern Rocky Mountain chain,
managing water runoff are again mentioned. where a small temperature rise reduces snowfall substan-
To summarize: tially, is the chance for increases of both the “drought of
1. Average annual rainfall will increase in some regions and record” and the “flood of record” in most areas 共Fig. 2兲
decrease in others. It is important to recognize, however, that 共Berry 1998; Pearce 2006; IPCC 2007兲.
the management of water allocation rarely is concerned only 3. The prediction of a rise in sea level due to climate change is
with the average annual flow that may be available. Rather, well known. Such a rise will have an impact on fresh water
the available water for many users, especially those in urban supplies, especially on groundwater supplies in coastal areas,
areas, requires a reliable and consistent source of water. The through increased saltwater intrusion 共Jackson et al. 2001;
prediction of more frequent heavier precipitation events and National Academy of Sciences 2001兲. A significant challenge
more frequent and/or intense extreme weather events sug- relates to wetlands during periods of decreased water avail-
gests that river flow may not be as dependable as historically ability. 共Johnson 1998兲.
experienced, disrupting for example the consistent delivery 4. The most vulnerable industries, settlements, and societies are
of urban water supplies or the availability of cooling water generally those in coastal and river flood plains, those whose
for the power industry. The alteration of natural flows will economies are closely linked with climate-sensitive re-
certainly affect the aquatic ecosystem, thereby disrupting sig- sources, and those in areas prone to extreme weather events,
nificant elements of the food chain that could have dramatic especially where rapid urbanization is occurring. Significant
effects. Water-based recreation will be affected. changes in average temperature, precipitation, and soil mois-
This conclusion gives further support to the 2001 predic- ture are very likely to affect demand in most sectors, espe-
tion that climate change will substantially reduce available cially in agricultural irrigation, forestry, power generation,
water in many of the water-scarce areas of the world, but will and municipal use 共National Academy of Sciences 2001兲.
increase it in some other areas. However, even in those areas 5. Local food supplies are projected to be adversely affected by
where precipitation is predicted to increase, much of the in- decreasing fisheries resources in large lakes due to rising
crease may occur in high intensity events. Flood magnitude water temperatures, which may be exacerbated by continued
and frequency could increase in many regions as a conse- overfishing.
quence of increased frequency of heavy precipitation events. 6. Increased deaths, disease, and injury due to heat waves,

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 floods, storms, fires, and droughts are expected. sity 共U.S. Advisory Commission 1991兲. In the case of a new
7. Management of water resources can reinforce mitigation of water sharing agreement being developed, some provisions of
global climate change and, in turn, may be affected by other adaptability of the new agreement to the uncertainties would be
mitigation measures. The call for energy efficiency and re- appropriate.
newable energy raises the discussion about the benefits and The need to adjust existing water sharing agreements to the
costs of hydropower. Increased use of navigation transport new uncertainties caused by climate change is complicated for a
may increase conflict among users, especially during drought variety of factors, many of which do not involve the actual in-
conditions when maintaining navigable channels may limit creased uncertainty itself. The parties to an existing agreement are
municipal water supply and irrigation. Reforestation, on the loath to change it if it has worked in the past. This reluctance to
other hand, may bring positive benefits to clean water and change is similar to that associated with grandfathered water
flood mitigation. rights holders who lay claim to their full share while “higher and
better” uses are issued junior rights with no certainty that they
will actually receive the water they need.
Impact of Climate Change on Transboundary Water Some existing transboundary water sharing agreements can be
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Sharing modified to accommodate climate change while others may need

to be replaced. The likelihood that an existing water sharing
Accurate and reliable data and information are key requirements agreement can be modified depends on the water sharing strategy
in effective water planning and management 共Dellapenna 1997; that underlies the agreement and the geographic region of the
Draper 1997; Vörösmarty 2002兲. With increasing variability as- subject source water. The various strategies for transboundary
sociated with climate change, existing water management prac- water sharing have been discussed in detail elsewhere 共McCor-
tices may prove less effective 共Vörösmarty 2002兲. Climate change mick 1994a,b; Kenney 1995; Draper 2001, 2006兲 and will only be
will affect water sharing in many of the same ways it will affect summarized here. The key issues to be considered are 共1兲 the
the management of water within a specific legal jurisdiction. impacts from climate change on water resources in the hydrogeo-
It has been argued that effective and efficient transboundary graphic region of the agreement; and 共2兲 how the risks associated
water sharing faces a number of obstacles. Among these is an with having insufficient source water is apportioned between the
incomplete knowledge of the timing and quantity of available parties.
source water to be allocated among the parties. In the past, pre- A large number of different water sharing strategies exists in
diction of the timing and quantity of water to be allocated was theory. However, as the historical record reveals, only a few of
based on the historical record. Future over-allocation due to an them have actually been used 共McCormick 1994a,b兲. Although
inaccurate historical record is illustrated by the 1922 Colorado some water sharing agreements do not fall into any one of these
River water allocation, which was based on the 30 years hydro- strategies and many compacts may contain elements of two or
logical record available at that time. Later research, based on an more strategies, they are representative of the approaches in use.
analysis of tree rings, determined that the amounts of water used Generally, five strategies have been applied in water sharing
in the allocation were abnormally high, resulting in over- agreements: 共1兲 priorities of use are set according to specific
allocation of the water source 共Stockton and Jacoby 1976; water demands, such as agricultural or municipal; 共2兲 limitations
Murakami 1995兲. Essentially, the accuracy of predictions of the are placed on water storage by upstream parties; 共3兲 delivery of a
future yield of shared water source leaves a significant uncertainty specific quantity of water by the upstream party is mandated at a
for developing an effective and efficient water sharing agreement particular location on the shared resource; 共4兲 the shared resource
共Tarlock 2000兲. In times of climate change, the historic record is divided among the parties according to a certain percentage of
may be unreliable as an indicator of future conditions 共Draper the flow; and 共5兲 comprehensive basin management in which an
2001, 2006兲. The underlying issue resulting from climate change independent commission, under supervision and policy control of
will be increasing the uncertainty of the quantity and timing of the the states involved, allocates water according to a predetermined
source water that may be available to be allocated among the objective function 共McCormick 1994a, b; Kenney 1995; Draper
parties. 2001, 2006兲.
This increased uncertainty from climate change can be accom- It should be noted that most water sharing agreements refer-
modated when new water sharing agreements are developed. For enced in the discussion below are in the western United States, in
an agreement on water sharing to be effective, it should be able to areas that either primarily depend on snow melt to provide the
adapt to potential changes in site-specific circumstances that may source water, or otherwise depend on very specific seasonal flows
develop within the time period the agreement is in effect that will be significantly disrupted by the impacts predicted by the
共Bernauer 2001兲. The provisions in the agreement should be suf- 2007 IPCC Assessment. If the predictions are correct, all of the
ficiently adaptable to allow them to evolve over time and to re- noted compacts will need to be modified or replaced.
spond to changes in the climatic, hydrologic, economic, social, The “priority of particular demand” allocation strategy sets
and even political conditions 共Eaux Partagee 2002; Fitch 2003兲. priorities by type of use rather than by user location within the
The agreement should be able to accommodate unexpected water basin, and provides certain quantitative limitations on those
changes in water source availability that may result from extreme priorities. The allocation of the risk of shortage is apportioned
events such as prolonged droughts and climate change. Likewise among types of users rather than hydrogeographic areas. Lower-
the agreement should be able to accommodate changes in the value uses, with lower priorities, bear the burden in a period of
demand for water that may arise from changes in the economic shortage. Compacts adopting this strategy in whole or in part
foundation of one or more of the parties or from sociological or include Costilla Creek Compact, 60 Stat. 246 共1946兲, amended 77
political changes in the value assigned to particular water de- Stat. 350 共1963兲; Bell Fourche Compact, 58 Stat. 94 共1944兲;
mands. As with any water management policy, the provisions and Kansas–Nebraska Big Blue River Compact, 86 Stat. 193 共1972兲;
rules within a water sharing agreement can best be developed and and Klamath River Basin Compact, 71 Stat. 497 共1957兲 共McCor-
implemented by retaining and encouraging innovation and diver- mick 1994a,b; Kenney 1995; Draper 2001, 2006兲. Clearly, this

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 general strategy, since it prioritizes demands in a fashion that allocation as each party shares in surplus or deficit in proportion
favors “grandfathered” uses, will not be simple to modify to re- to its allocated percentage. Compacts adopting this strategy in
spond to reduced yield. Any modification may leave some users whole or in part include Upper Colorado River Basin Compact,
without the source water necessary to meet the demand. Any at- 63 Stat. 31 共1949兲; La Plata River Compact, 43 Stat. 796 共1925兲;
tempts at compact replacement will have to contend with signifi- Yellowstone River Compact, 65 Stat. 663 共1950兲; Snake River
cant political and economic forces. Strategies to augment the Compact, 64 Stat. 29 共1949兲; Red River Compact, 94 Stat. 3305
available source water from outside the particular basins may be 共1980兲; and Belle Fourche River Compact, 58 Stat. 94 共1944兲
technically feasible but such a strategy of interbasin transfer 共or 共McCormick 1994a,b; Draper 2001, 2006兲. This strategy is the
additional interbasin transfer兲 would itself be politically difficult least likely to be severely strained by the impacts of climate
and raise the cost of water dramatically 共Draper 2004兲. change. The difficulty of using this strategy is the lag time be-
A “storage limitation” strategy limits the amount of water that tween gathering the hydrologic data and translating the percent-
an upstream entity may impound annually, seasonally, or other age withdrawal rate into actual volumetric extraction.
time period base. With regard to risk allocation, the downstream Finally, transboundary water allocation may be part of “com-
party assumes the majority of the risk because stream flow may prehensive basin management.” In this alternative, an indepen-
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not be sufficient to do more than fill upstream reservoirs. Adding dent commission, under supervision and policy control of the
users upstream may further diminish flow available downstream. states involved, is given the regulatory authority to manage all 共or
Finally, the downstream party assumes the risk of shortage during most兲 water-related aspects of the basin to include water supply,
prolonged periods of drought or during flood control operations. pollution control, flood protection, watershed management, recre-
Compacts adopting this strategy in whole or in part include Rio ation, hydroelectric power, regulation of withdrawals and diver-
Grande Compact of 1938, 53 Stat. 785, 938; Arkansas River sions, intergovernmental relations, capital financing, and planning
Compact, 63 Stat. 145 共1949兲; Arkansas River Basin Compact of and budgeting. Compacts adopting this strategy include the Dela-
1965, 80 Stat. 1409 共1966兲; Canadian River Compact, 66 Stat. 74 ware River Basin Compact 共DRBC兲, Pub. L. 87-328, 75 Stat. 688
共1952兲; Bear River Compact, 72 Stat. 38 共1955兲, amended 94 共1961兲; and the Susquehanna River Basin Compact, Pub. L. No.
Stat. 4, Art. XIII 共2兲 共1980兲; Kansas–Nebraska Big Blue River 91-575, 84 Stat. 1509 共1970兲 共McCormick 1994a, b; Draper 2001,
Compact, 86 Stat. 193 共1972兲; and Upper Niobrara River Com- 2006兲. By its very nature, the parties that face the greatest risk are
pact, 83 Stat. 86, Art. V 共1969兲 共McCormick 1994a,b; Kenney those water users that are not favored by either the terms of the
1995; Draper 2001, 2006兲. The impact of climate change as pre- compact or the policies of the independent commission.
dicted by the IPCC will increase the downstream party’s risk.
Modification of the compact can come only at the expense of the
upstream party, making negotiations difficult at best. Transboundary Water Sharing Agreements at Risk
Under a “guaranteed quantity at a point,” or “minimum flow,”
strategy, a guaranteed quantity of water is to be delivered at cer- IPCC describes regional, vulnerability, and key concerns by re-
tain points. The upstream party guarantees that a fixed amount of gion 共IPCC 2007兲. Therefore, the transboundary water sharing
water will pass a certain point every year or other time periods. agreements most at risk can be identified by the geographical
The risk of water shortage falls upon the upstream parties, which region in which the subject source water is located. The Trans-
guarantee the minimum flow, although the upstream parties may boundary Freshwater Dispute Database lists over 400 interna-
also obtain benefit of extra water in periods when stream flow tional freshwater agreements 共Fig. 3兲. Of these, approximately
exceeds the base amount. To modify the division of risk, the one-quarter directly involve water quantity to some degree
parties may agree to divide any surplus over a specified minimum 共Transboundary Freshwater Dispute Database, www.transbound-
flow so that both upstream and downstream parties share part of arywaters.orst.edu兲. While the discussion below relates only to
the surplus. Alternatively, the risk assumed by the upstream party those agreements involving water quantity as their major focus, it
may be lessened by limiting what it should do to ensure the mini- should be recognized that freshwater agreements involving water
mum flow. Compacts adopting this strategy in whole or in part quality, hydropower, and navigation may also be at risk.
include Colorado River Compact, approved 45 Stat. 1057 共1928兲; When classifying the risks that challenge transboundary water
Rio Grande Compact of 1938, 53 Stat. 785, 938; Arkansas River sharing agreements, it must be understood that all risks are rela-
Basin Compact of 1965, 80 Stat. 1409 共1966兲; Bear River Com- tive. The IPCC Reports, as well as other researchers in the field,
pact, 72 Stat. 38 共1955兲, amended 94 Stat. 4, Art. XIII 共2兲 共1980兲; project a general across-the-board risk in all regions. For the re-
South Platte River Compact, 44 Stat. 195 共1923兲; Sabine River gions that face the highest risk, predictions include both a dra-
Compact, 68 Stat. 690 共1953兲; and Colorado River Compact, ap- matic reduction in the amount of precipitation the region may
proved 45 Stat. 1057 共1928兲 共McCormick 1994a, b; Kenney 1995; experience as well as seasonal variations in the frequency and
Draper 2001, 2006兲. Clearly, this type of compact will be difficult intensity of storm events. Those regions that face the lowest risk
to modify since the increased uncertainty of flows increases the may experience only a change in seasonal variations in the fre-
risks of the upstream party’s ability to meet their obligations. quency and intensity of storm events, with the amount of precipi-
With the “percentage of flow” strategy, the parties allocate tation on an annual basis being little changed while reliability
water by either a fixed percentage or a formula based on different may be greatly compromised.
flow levels. Each participant is entitled to take its specified per-
centage of the flow. If existing allocations are not grandfathered,
Africa
those existing rights may be impaired if the allocated percentage
results in insufficient water for those rights. In some jurisdictions, “By 2020, between 75 and 250 million people are projected to be
this could result in legal “takings” claims. This strategy should exposed to an increase of water stress due to climate change. If
include provisions for instream flow maintenance, which may re- coupled with increased demand, this will adversely affect liveli-
sult in less usable water than the strict percentages might indicate. hoods and exacerbate water-related problems.” The 2001 Report
The method is, however, relatively benign with regard to risk concluded that major rivers of Africa are highly sensitive to cli-

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Downloaded from ascelibrary.org by University of Leeds on 05/17/15. Copyright ASCE. For personal use only; all rights reserved.

Fig. 3. 共Color兲 Projected precipitation 共R. K. Pachauri and B. Jallow, with permission, www.ipcc.ch兲

mate variation and warned that average runoff and water avail- southern African coast would be adversely impacted by sea-level
ability would decrease in the Mediterranean and southern coun- rise through inundation and coastal erosion. It should be noted,
tries of Africa. however, that climate change models for the central Africa region
Relative changes in precipitation 共in percent兲 for the period vary considerably in their predictions.
2090–2099, relative to 1980–1999. Values are multimodel aver- Twenty of the transboundary water supply agreements listed in
ages based on the SRES A1B scenario for December to February the Transboundary Freshwater Dispute Database are located in
共left兲 and June to August 共right兲. White areas are where less than the African continent. Based on the conclusions of the 2007 IPCC
66% of the models agree in the sign of the change and stippled Assessment, but recognizing the caveat for central Africa, all
areas are where more than 90% of the models agree in the sign of water sharing agreements are at risk. Especially significant are
the change. those involving the Nile River. Most of these can be considered
“Agricultural production, including access to food, in many colonial-era agreements that are outdated. In 1998, all Nile ripar-
African countries and regions is projected to be severely compro- ian states except Eritrea began discussions about a regional part-
mised by climate variability and change. The area suitable for nership to better manage the Nile. This Nile Basin Initiative in-
agriculture, the length of growing seasons and yield potential, cluded the countries of Burundi, Sudan, Tanzania, Uganda, the
particularly along the margins of semiarid and arid areas, are
Democratic Republic of Congo, Egypt, Ethiopia, Kenya, and
expected to decrease. This would further adversely affect food
Rwanda 共The Nile 2003兲. Given the potential severe impacts from
security and exacerbate malnutrition in the continent. In some
climate change, this initiative should place climate change high
countries, yields from rain-fed agriculture could be reduced by up
on the agenda as a new regional water sharing agreement is
to 50% by 2020.
developed.
Local food supplies are projected to be negatively affected
by decreasing fisheries resources in large lakes due to rising
water temperatures, which may be exacerbated by continued Asia
overfishing.”
The 2001 IPCC Report warned that coastal settlements in the “Glacier melt in the Himalayas is projected to increase flooding,
Gulf of Guinea, Senegal, Gambia, Egypt, and along the east– rock avalanches from destabilized slopes, and affect water re-

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J. Water Resour. Plann. Manage. 2007.133:405-415.

 sources within the next two to three decades. This will be fol- land to the Bay of Plenty 共New Zealand兲, are projected to exac-
lowed by decreased river flows as the glaciers recede. erbate risks from sea-level rise and increases in the severity and
Freshwater availability in central, south, east, and southeast frequency of storms and coastal flooding by 2050.
Asia particularly in large river basins is projected to decrease due Production from agriculture and forestry by 2030 is projected
to climate change which, along with population growth and in- to decline over much of southern and eastern Australia, and over
creasing demand arising from higher standards of living, could parts of eastern New Zealand, due to increased drought and fire.
adversely affect more than a billion people by the 2050s.” The However, in New Zealand, initial benefits to agriculture and for-
2001 IPCC Report warned that extreme events would increase in estry are projected in western and southern areas and close to
temperate and tropical Asia, including floods, droughts, forest major rivers due to a longer growing season, less frost, and in-
fires, and tropical cyclones. Runoff and water availability is ex- creased rainfall.
pected to decrease in arid and semiarid Asia but increase in north- Although no international water sharing agreements are rel-
ern Asia. Sea-level rise and an increase in the intensity of tropical evant to Australia, the country’s National Water Initiative will
cyclones would displace tens of millions of people in low-lying face significant risks of reduced freshwater availability. This will
coastal areas of temperate and tropical Asia and increased inten- cause significant disruption to the program for permanent trades
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sity of rainfall would increase flood risks in these areas. in water and its intended expansion. Water recovery efforts in the
“Coastal areas, especially heavily populated megadelta regions Murray–Darling Basin Water Agreement may be compromised
in south, east, and southeast Asia, will be at greatest risk due to 共Australian Government 2006兲.
increased flooding from the sea and in some megadeltas flooding
from the rivers.
Endemic morbidity and mortality due to diarrhoeal disease Europe
primarily associated with floods and droughts are expected to rise “Negative impacts will include increased risk of inland flash
in east, south, and southeast Asia due to projected changes in floods, and more frequent coastal flooding and increased erosion
hydrological cycle associated with global warming. Increases in 共due to storminess and sea level rise兲. Mountainous areas will
coastal water temperature would exacerbate the abundance and/or face glacier retreat, reduced snow cover and winter tourism, and
toxicity of cholera in South Asia.” extensive species losses 共in some areas up to 60% under high
Forty-one transboundary agreements primarily dedicated to emission scenarios by 2080兲.” The 2001 Report warned that river
shared water supply exist in the Asian continent. The 2007 IPCC flood hazards will increase across much of Europe and in coastal
Reports show the 15 water sharing agreements in western Asia areas, risk of flooding, erosion and wetland loss would increase
共Middle East兲 at significant risk because of projected estimates of substantially with implications for human settlement, industry,
reduced yields in the future. tourism, agriculture, and coastal natural habitats.
Although freshwater availability in central Asia is projected to “In southern Europe, climate change is projected to worsen
decrease, data are inconclusive with regard to the region in and conditions 共high temperatures and drought兲 in a region already
around the four water sharing agreements to which Kazakhstan is vulnerable to climate variability, and to reduce water availability,
party. hydropower potential, summer tourism, and in general, crop
Reduction in freshwater availability in south Asia will occur as productivity.”
a general rule but must be seasonally adjusted. Models suggest A number of international water supply or joint management
that the monsoon season, June–September, will remain stable but agreements exist in the southern Europe region of high risk. Most
extremely dry periods may occur during other seasons. The agree- agreements are quite river or lake specific except the 1968 treaty
ments should be modified as necessary and should place more between Bulgaria and Turkey which calls for cooperation in the
emphasis on stored water for the support need in the dry periods. use of shared waters. Because climate change is expected to be
The water sharing agreements between India and Bangladesh are especially significant 共similar to northern Africa兲 in southern Eu-
at great risk and may cause increased tensions. Although reduced rope riparian to the Mediterranean these treaties will probably
freshwater in the Ganges–Brahmaputra–Meghna basin may re- require extensive modification or replacement.
duce freshwater flooding in southern Bangladesh, sea level rise is “In central and eastern Europe, summer precipitation is pro-
projected to more than offset this with salt water flooding. jected to decrease, causing higher water stress. Health risks due to
The monsoon season in southeast Asia occurs during the pe- heat waves are projected to increase. Forest productivity is ex-
riod December–March, when the models predict a significant re- pected to decline and the frequency of peatland fires to increase.”
duction in precipitation. Thus, the Mekong initiative faces high A number of international water supply or joint management
risks. agreements, ranging from the Rhine River Basin in the west to the
Northeast Asia will have less deviation in precipitation and the Vistula River in the east, are located in this region of medium
water sharing agreements for the Amur Basin, between China and risk. While most are very site specific treaties that involve navi-
Mongolia, face limited risk. gation, water quality, or hydropower, a limited number involve
joint use of transboundary, or frontier, waters. In these cases,
Australia and New Zealand whether the agreement can be modified to conform to the pre-
dicted climate changes or must be replaced depends on the ad-
“As a result of reduced precipitation and increased evaporation, ministrative apparatus contained in the treaty 共see Draper 2006兲.
water security problems are projected to intensify by 2030 in The 1958 agreement between Czechoslovakia and Poland may
southern and eastern Australia and, in New Zealand, in northland require two replacement treaties due to the recent separation of
and some eastern regions.” This is a change from the 2001 IPCC the Czech Republic and Slovakia. Models suggest that the periods
Report which warned of increases in the intensity of heavy rains of reduced precipitation may peak in the summer months and
and tropical cyclones. return to less drastic reductions in the late fall and winter. Em-
Ongoing coastal development and population growth, in areas phasis on stored water may be required to meet demands in the
such as Cairns and southeast Queensland 共Australia兲 and north- summer months. This should be built into the water sharing

412 / JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / SEPTEMBER/OCTOBER 2007

J. Water Resour. Plann. Manage. 2007.133:405-415.

 agreements. The 1994 Convention on cooperation for the protec- value of infrastructure in coastal areas increase vulner-
tion and sustainable use of the River Danube is at high risk, ability to climate variability and future climate change,
primarily because the lower basin will be affected in a manner with losses projected to increase if the intensity of tropical
similar to basins in the Mediterranean fringe. The precipitation storms increases.
forecasts for the upper basin are similar to other basins in central
Europe. The 2001 IPCC Report warned that a sea-level rise 5 mm/ year
“In northern Europe, climate change is initially projected to 共0.2 in.兲 would result in enhanced coastal erosion, coastal flood-
bring mixed effects, including some benefits such as reduced de- ing, loss of coastal wetlands, and increased risk from storm
mand for heating, increased crop yields, and increased forest surges, particularly in Florida and much of the U.S. Atlantic coast.
growth. However, as climate change continues, its negative im- As a general rule, the agreements at high risk are international
pacts 共including more frequent winter floods, endangered ecosys- transboundary agreements between the United States and Mexico,
tems, and increasing ground instability兲 are likely to outweigh its as well as interstate water sharing agreements 共compacts兲 in the
benefits.” southwestern and midwestern tiers of states. Agreements between
Transboundary water sharing agreements in the northern the United States and Canada will be at relative low risk as will
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fringes are at limited risk. be interstate compacts in the east. The effect of snowmelt will
have an adverse effect along the continental divide, north from
Arizona and New Mexico to Alaska 共Brown 2007兲.
Latin America
Recent warming and changes in atmospheric circulation
“By midcentury, increases in temperature and associated de-
patterns over North America have resulted in reductions
creases in soil water are projected to lead to gradual replacement
in the duration of the snow cover season, the amount of
of tropical forest by savanna in eastern Amazonia. Semiarid veg-
etation will tend to be replaced by arid-land vegetation. water stored in the snowpack, as well as a widespread
In drier areas, climate change is expected to lead to saliniza- trend toward earlier spring melt. These changes are par-
tion and desertification of agricultural land. Productivity of some ticularly pronounced over western Canada . . . where
important crops are projected to decrease and livestock produc- spring melt has advanced at a rate of close to half-a-day
tivity to decline, with adverse consequences for food security. In per year over the period since 1955. Reduced storage of
temperate zones soybean yields are projected to increase.” The water in the snowpack and earlier melt translate to a
2001 IPCC Report warned that floods and droughts would be- lower fresh water pulse for recharge of soil moisture and
come more frequent with floods increasing sediment loads and reservoirs, and increased potential for evaporation loss.
degrading water quality in some areas. This trend, coupled with increasing demand for water,
. . . Sea-level rise is projected to cause increased risk of flood- suggests increasing conflict in the use and management of
ing in low-lying areas. Changes in precipitation patterns and the snowmelt-derived water supplies.
disappearance of glaciers are projected to significantly affect
water availability for human consumption, agriculture, and energy The major risk in North America lies to those agreements that
generation. . . . involve river basins whose rivers rely as a major contribution on
As with central Africa, it must be noted that climate change snow melt. The 2007 IPCC Working Group II contribution reports
models for South America vary considerably in their predictions, that there is “high confidence” of “increased run-off and earlier
especially for the winter months. That being said, of the two spring discharge in many . . . snow-fed rivers” 共WGII 2007兲. As
major transboundary basins in South America, only the La Plata an example, water users of the upper and lower Colorado River
has an agreement that is directly related to water supply. All may basins may find that, because of the lack of snow loads in the
be at high risk due to a projected reduction of precipitation, at headwaters of the basins, the source water needed to support ag-
least in the summer and fall. The 1978 Treaty for Amazonian riculture in the basins during the growing season is greatly re-
cooperation that may involve water supply will, however, be at duced. The increase in evaporation will negatively affect the abil-
high risk due to the expected aridity. ity to store water for future use in surface reservoirs. Independent
modeling has reported effects on shared waters in the western
United States that supports this conclusion 共Stewart et al. 2004兲.
North America
Spring snowmelt is the most important contribution of
“Moderate climate change in the early decades of the century is many rivers in western North America. If climate
projected to increase aggregate yields of rainfed agriculture by
changes, this contribution may change. A shift in the tim-
5–20%, but with important variability among regions. Major chal-
ing of springtime snowmelt towards earlier in the year
lenges are projected for crops that are near the warm end of their
already is observed during 1948–2000 in many western
suitable range or depend on highly utilized water resources.
Warming in western mountains is projected to cause decreased rivers. . . . Streamflow timing changes for the 1995–2099
snowpack, more winter flooding, and reduced summer flows, ex- period are projected 共to be兲 strongest in the Pacific North-
acerbating competition for over-allocated water resources.” The west, Sierra Nevada, and Rocky Mountains, where many
2001 Report warned that snowmelt-dominated watersheds in rivers eventually run 30–40 days earlier.
western North America will experience earlier spring peak flow The earlier spring streamflow timing will cause a significant
reductions in summer flows and reduced lake levels and outflows economic disruption since peak demand for irrigated agriculture
of the Great Lakes–St. Lawrence under most scenarios. occurs in the summer. Each summer will be a continuing struggle
Coastal communities and habitats will be increasingly for available water between farming and urban water supply.
stressed by climate change impacts interacting with devel- More importantly, as to the effectiveness of the transboundary
opment and pollution. Population growth and the rising water sharing agreements, significant disputes may arise because

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J. Water Resour. Plann. Manage. 2007.133:405-415.

 upstream parties may be unable to meet their obligations to down- Draper, S. E., ed. 共2006兲. Sharing water in times of scarcity: Guidelines
stream parties or downstream parties will not receive their ex- and procedures in the development of effective agreements to share
pected allocation. water across political boundaries, ASCE, Reston, Va.
Eaux Partagées 共Shared Water兲 Working Group of the French Académie
de l’Eau 共Eaux Partagées兲. 共2002兲. Proposals for a strategic guide to
assist in the constitution of international interstate commissions for
Concluding Thoughts shared water resources, Draft, 具www.inbo-news.org/divers/thonon/
AcademieRiobGuide_gb.PDF典 共Jun. 9, 2003兲.
There is little dispute that climate change is occurring as this Fitch, E. 共2003兲. “Introduction: Social foundations of water manage-
article is written. A consensus exists among scientists that climate ment.” Water Resour. Impact, 5共6兲, 3–4.
change is accelerating because of human influence. There is, of Hahn, M., and Palmer, R. 共2001兲. Climate impacts on PNW municipal
course, a divergent view that explains the causes of climate water supplies, Dept. of Civil and Environmental Engineering, Univ.
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