Response of the Rio Grande and shallow ground water in the Mesilla bolson to irrigation climate stress, and pumping

摘要

The El Paso-Ciudad Juarez metropolitan areaobtains its water from the Rio Grande and inter-montane-basinaquifers. Shallow ground water in this region is in closecommunication with the surface water system. A major problemwith both systems is salinity. Upstream usage of the water in theRio Grande for irrigation and municipalities has led toconcentration of soluble salts to the point where the surface watercommonly exceeds drinking water standards. Shallow groundwater is recharged by surface water (primarily irrigation canals andagricultural fields) and discharges to surface water (agriculturaldrains) and deeper ground water.The source of water entering the Rio Grande varies seasonally.During the irrigation season, water is released from reservoirs andmixes with the return flow from irrigation drains. During the non-irrigation season (winter), flow is from irrigation drains and riverwater quality is indicative of shallow ground water. The annualcycle can be ascertained from the inverse correlation between ionconcentrations and discharge in the river. Water-quality dataindicate that the salinity of shallow ground water increases eachyear during a drought.Water-management strategies in the region can affect waterquality. Increasing the pumping rate of water-supply wells willcause shallow ground water to flow into the deeper aquifers anddegrade the water quality. Lining the canals in the irrigation systemto stop water leakage will lead to water quality degradation inshallow ground water and , eventually, deep ground water byremoving a major source of high quality recharge that currentlylowers the salinity of the shallow ground water.