Additionally, pumping in the intermediate and deep Mesilla Bolson aquifers has affected ground-water flow by causing the downward migration of brackish ground water from the shallow aquifer. This study documents and analyzes the relationship between the water quality, discharge, and source waters of the Rio Grande in the El Paso area. The approximately 60-year record of discharge for the Rio Grande at El Paso is shown in Figure 3. Higher discharges are shown in the darker shades. Black areas near the right side of the graph represent time periods with no available data.
Several trends emerge from the data.
The irrigation season extends from March to October and would have season values of 0.2 to 0.8 in Figure 3. In a normal year, the majority of the rainfall in the upper Rio Grande Valley falls between July and October, season values of 0.5-0.8. These trends are visible in Figure 3. Multi-year variations in precipitation are also visible. Darker vertical bands represent wetter years where lighter vertical bands represent dry years.