Aggregate water availability for energy development in the upper Colorado River basin

Abstract

Can a large (significant in national terms) energy-recovery industry be developed in the Upper Colorado River Basin (UCRB), alongside more traditional water uses, without causing a problem in the aggregate quantity of water supplied to the Lower Colorado River Basin?. This report answers that question in a "reasonably conservative" manner by slightly overpredicting demand and underpredicting supply. First, aggregate consumption of water in the UCRB due to water intensive energy industries is calculated as a function of the level of energy production. Reasonably conservative (i.e., on the high side) estimates of unit water requirements for coal-electric generation, coal-slurry pipelines, coal gasification (to produce substitute natural gas — SNG), and oil-shale processing are developed from an extensive literature survey. These are combined with various energy-development scenarios, also developed from a literature survey, to give total energy-related water consumption as a function of total energy industry size. Overall total UCRB water consumption can then be found by adding to the energy-related water use all non-energy-related consumption. On the supply side, aggregate UCRB water availability is determined from the results of a steady-state, stochastic hydrologic model which predicts the reliability of flow to the lower basin as a function of total UCRB consumption. Predictions of the model are conservative, in the sense of being on the low side, because: (1) the period of record used to determine tributary flows is a relatively low flow period and (2) because the use of excess stored water above steady-state levels during transition periods to steady state is ignored. Demand and supply are then presented together in a graphical form which allows the reader to determine for him-or-herself the level of energy development which can be allowed in the UCRB, depending on the levels he or she chooses for non-energy-related water consumption in the upper basin and the reliability of water supply to the lower basin. On an aggregate basis, there appears to be enough water available in the Upper Colorado River Basin to produce about 7 quads per year (7 x 10^(15) Btu/yr or 7.4 x 10^(18) J/yr, equivalent to well over one-half current liquid fuel imports) from the region's fossil fuel resources by water-intensive energy industries and still allow an increase in other water uses by more than 25% (about 0.8 million acrefeet per year (9.8x10^8 m^3/yr)) over what they now are.

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