"I've always thought it strange that drawing a political line across a landmass somehow stopped the water flowing."
(John Pigram, personal communication to William Turner, May 11, 2001)

Climate is what you expect, weather is what you get.
(Robert Heinlein, 1973, Time Enough For Love)

Climate lasts all the time and weather only a few days
(Mark Twain, English As She Is Taught)

ABSTRACT

Interstate Stream Compacts within the United States are federal statutes that allocate surface water among basin states. They are inflexible in their result. The State of New Mexico is party to seven Interstate Stream Compacts, for example. The allocation of water is based on past surface water flow records measured in the early to mid-20th Century before the onset of climatic change had yet to take effect. 

Climatic changes will undoubtedly affect the geospatial and temporal distribution of rainfall in as yet unforeseen ways. It is likely that because of new geospatial and temporal distribution of rainfall that the flow records on which the compacts were based will no longer be valid. With regard to the compacts, this has gone unrecognized in the United States and in particular the arid American West. Downstream states will behave inflexibly in requiring upstream states to make required deliveries even in the face of diminishing water resources available in the upstream states.  Legal and institutional changes must be made to accommodate climatic change to ensure flexible apportionment between basin states.

GEOPOLITICAL CONSIDERATIONS

Flowing water knows no political boundaries. The allocation of water between statal boundaries is complex and is commonly based on old quantitative hydrological data.  After an allocation of water is made between basin states, the allocation becomes set in concrete.  There is little consideration given to modification of compacts and treaties should the flow regime of a river change.   Though private water users may be willing to sell their own private rights to a neighboring states, the state does not recognize the result of the private transaction as affecting the requirement of a neighboring basin state to make the deliveries called for in the compact or treaty.

Deviations of states from the terms of compacts between states within nations are dealt with by the national judicial system considering the legal systems that govern water use within each of the contesting states and according to principles of international water law.

Deviation of nations from treaties governing the allocation of water are commonly much more difficult to deal with because there is no enforcement mechanism apart from the goodwill of the neighboring nations.  Mexico was supposed to repay the United States with 1.4 million acre feet of water by September 30, 2001 that they had overdiverted since 1992. They will not.

CLIMATIC CHANGE

When, because of changing demographics and uses, water shortages appear within a state the only alternatives are technical or shifts in public policy with regard to utilization of the allocated resource.  The problems are commonly intractable because of the large number of hydrohegemons. 

The magnitude of the water resource when compacts or treaties were negotiated and placed into force is regarded as randomly variable about a long-term average flow determined by antecedent flow records.  What happens when the long-term average flow is no longer average but decreases in some random manner along a monotonically decreasing trend?  Such is the feared situation that will occur as the climate of the earth warms. 

Climatic change has long been recognized anecdotally in modern times (Windham, 1741)

Climatic change has been looked at in historic and prehistoric time since at least 1914 when Pettersson published on the subject.  Plass in 1956 and 1957 may have been the first to advance the theory of climatic change. 

Simply put, the climate warms because the earth is a black-body radiator.  That is, the wavelength of electromagnetic radiation passing through the earth's atmosphere that heats the earth during the day is much shorter than the wavelength of the radiation emitted back to cold space at night.  The long wavelength infrared terrestrial back-radiation in the 12 to 18 micron range of the electromagnetic spectrum is captured by carbon dioxide gas and retained in the atmosphere leading to elevated atmospheric temperature.   The process is nearly irreversible and it has taken more than 40 years to be taken very seriously.

The effects of global warming on the regional and local hydrology is variable in ways that may lead to geospatially differential distribution that is dissimilar from the distribution upon which compacts and treaties were developed.   This may lead to increased hardship in one locale and abundance in others.  It may result in states being unable to meet downstream delivery commitments.

For example, the Rio Grande watershed begins at higher elevations in southern Colorado where most of the water comes from winter snow.  With more moisture in the atmosphere as a result of global warming, the high Rocky Mountains of Colorado may have more snow.  It is likely, however, that the snowpack will melt earlier and the Upper Rio Grande.  The deliveries of water to Texas at Elephant Butte Dam downstream are set at an average of 790,000 acre feet per year over a moving ten-year period.  The New Mexico deliveries are based on a percentage of the flow over the Otowi gaging station at Espanola in Northern New Mexico, the dividing line between the Upper Rio Grande and the rest of the Rio Grande.  If flows at Otowi are high then New Mexico's deliveries to Texas at the San Acacia gaging station at Elephant Butte must be high. All snowmelt in the Spring is passed downstream to Elephant Butte Reservoir.

However, because New Mexico below Otowi is at lower elevations, water inflow from tributaries below Otowi may be reduced because the net surface water deficit has increased and there is insufficient rainfall to satisfy soil-moisture requirements before runoff can occur.  Therefore, there may be decreased surface water inflow during the summer months when the Middle Rio Grande below Otowi receives most of its normal rainfall.

Consequently, earlier springtime of water into Elephant Butte result in a longer period of surface water evaporation and decreased summertime surface runoff south of Otowi can lead to greater water shortages and the inability of New Mexico to make its deliveries to Texas.  Evaporation from Elephant Butte is chargeable to the New Mexico reach of the Rio Grande. 

New Mexico can do nothing except buy up water rights along the Rio Grande to bypass water.  This diminishes the agricultural economy and limits growth of New Mexico.  The long-term result is to drive people out of the state in pursuit of the water: either upstream to Colorado or downstream to the sea where desalination plants may be the ultimate solution.  The result is a complete dislocation of people and their way of life.  If these dislocations are inevitable as seems to be developing in South Texas, it is necessary for government to plan for them to alleviate human suffering.

CONCLUSION

Compacts and treaties ignore the physical realities of the hydrological cycle and global warming.   The U.S. Supreme Court has supported the principle of equitable apportionment of water between basin states.  It is time to consider the effect of global warming and begin making the argument for holistic basinwide management and the principle of "flexible allocation."

REFERENCES

Pettersson, O., 1914, Climatic Variations in Historic and Prehistoric Time.   Svenska Hydrogr. Bio. Komm., Skriften, vol. v.

Plass, G.N., 1956, Effect of Carbon Dioxide Variations on Climate. Am. J. Phys. 24: 376-387.

Plass, G.N., 1957, The Carbon Dioxide Theory of Climatic Change, pp. 81-92.  In Recent Research In Climatology.  Committee on Research in Water Resources, University of California, La Jolla.

A 1741 letter from a Mr Windham, cited in Grove, J. M., The Little Ice Age, Methuen, 1988, p 112

DR. WILLIAM M. TURNER

Dr. Turner is a consulting hydro geologist and water resources expert with 40 years of worldwide experience. He has been dealing in water and water rights and water-related transactions for 35 years. He is the present Trustee for Natural Resources for the State of New Mexico and a member of the Governor's Task Force on Water in New Mexico. Dr. Turner is also an oil and gas operator and a licensed real estate broker. He operates the WaterBank.Com website. WaterBank.Com is the largest and most active listing service and marketplace for all manner of water assets on the Internet. He is currently working on water-related or water-technology transactions throughout the United States, Europe and Asia.

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