HR: 17:00h
AN: H14E-05    [Abstracts]
TI: Groundwater Recharge Evaluation in Semi-Arid Northeast Mexico in Response to Projected Climate Change
AU: * Wolaver, B D
EM: brad_wolaver@yahoo.com
AF: The University of Texas at Austin, Department of Geological Sciences, Jackson School of Geosciences, 1 University Station, C1100, Austin, TX 78712, United States
AB: This research evaluates the effects of projected climate change on mountain recharge in the semi-arid Cuatrocinegas Basin (CCB) of northeast Mexico. The CCB UNESCO Biosphere Reserve is located in Coahuila, Mexico (~27° N, ~102° W) and includes > 500 springs that discharge from a regional flow system to wetlands with > 70 endemic species and to an irrigation network. This study tests the hypothesis that projected climate changes will reduce CCB recharge. In CCB, ~75% of annual precipitation (~220 mm at 700 m, ~400 mm at 2350 m) falls between May and October and ~40% falls during the North American Monsoon in June, July, and August. Environmental isotopes indicate aquifer residence times of > 50 years. Stable isotopes (O and H) show that mountain precipitation (at an elevation of ~1170 to 2350 m) dominates groundwater recharge. Recharge is insignificant at lower- elevation valleys that cover the majority of the study area due to high evapotranspiration rates. A Cl^--balance water-budget recharge analysis estimates a spatially distributed recharge rate of ~1 to 3% of precipitation to provide at least 35x10⁶ m³/year spring discharge (as measured in canals that drain dozens of springs). IPCC AR4 climate projections predict an annual temperature increase of 3.0 to 3.5°C and an annual precipitation decrease of 5 to 10% for Subregion CNA (located adjacent to CCB) by 2099. During June to August, models project a temperature increase of 3.5 to 4.0°C and a precipitation increase of 0 to 5%. Although global and regional circulation models evaluate mountain regions poorly, a first-order evaluation of climate projections on CCB recharge is needed input to develop effective long-term groundwater management policies. Climate projections suggest that the minimum elevation at which recharge occurs in CCB may increase by ~615 m to 1785 m, which would limit recharge to the highest mountain elevations. If annual precipitation is reduced by 5 to 10% and temperatures increase as predicted, recharge may be significantly reduced, but relatively long aquifer flow paths may delay these effects on spring flow. Ultimately, a combination of reduced mountain recharge and higher valley evapotranspiration would reduce the size of groundwater-dependent wetlands and limit agricultural diversions.
DE: 1807 Climate impacts
DE: 1817 Extreme events
DE: 1829 Groundwater hydrology
DE: 1876 Water budgets
DE: 1880 Water management (6334)
SC: Hydrology [H]
MN: 2007 Fall Meeting