Interpretation of the potentiometric surface along the Rio Grande at selected locations in Albuquerque, New Mexico

A Professional Project submitted in partial fulfillment of the requirements for the degree of Master of Water Resources, Water Resources Program, University of New Mexico.The U.S. Geological Survey installed over 240 piezometers and 27 surface-water gages along the Rio Grande in Albuquerque, NM from 2003 to 2009, to monitor groundwater and surface-water levels and water temperatures. Spanning a 20 mile distance between the bridges at Alameda Blvd. and Interstate 25, there were 8 selected locations each consisting of paired east-west transects situated perpendicular to the river (Figure 1). Paired transects comprise two parallel cross-sections of the Rio Grande inner valley that were positioned approximately 500 ft. apart and extend to the riverside drains on both sides of the river. Each transect consisted of piezometers installed at various depths along the riverside drains, and in the Rio Grande riparian zone known as the bosque, and also included surface-water-stage gages installed in the Rio Grande and at both riverside drains. In the riparian zone, riverside piezometers were situated within 20 ft of the river bank whereas bosque piezometers were placed about halfway between the river bank and the riverside drain. Each transect contained piezometers along the river-side of the east and west riverside drains, on the side closer to the river and many of the transects contained piezometers located outside of the drains. Six transects contained piezometers located over 300 ft from the river. Every groundwater and surface-water site was instrumented with an electronic pressure transducer programmed to collect hourly water-level data. Depth to water data were processed through the USGS Automated Data Processing System (ADAPS) and later converted to water surface elevation. These water level elevations were then used to calculate horizontal and vertical groundwater gradients as related to seasonal variations in surface-water discharge in the Rio Grande. It is shown in this study that seasonal extremes of discharge significantly influence the direction and magnitude of groundwater gradients in the bosque. This study calculated hydraulic gradients at eight approximately equidistant locations in the study area, on both sides of the river, and from the river to the outside of both riverside drains at most locations. Gradients near the drains are particularly important because groundwater leakage from the river may at times flow at levels significantly below the drain invert elevations. When groundwater levels adjacent to the drains are well below the drain invert elevations, the drains cannot be recharged with river leakage - in fact, the drains here are implied to be losing surface water flow down into the groundwater system. There are likely several reasons for this. Pumpage from nearby municipal production wells may intermittently lower adjacent groundwater levels enough along drains to cause this. In addition, river water diverted out of the Rio Grande through the San Juan-Chama Drinking Water Project may reduce channel discharge and consequent leakage to the groundwater system enough to lower water levels in drain reaches as well as in the bosque through much of the Albuquerque area. Additionally, vertical and horizontal gradients at three locations in this study were analyzed for changes due to the influence of municipal production well pumpage from three of the nearest Albuquerque well fields. Other contributing factors to declining groundwater levels likely include climate change, bosque vegetation, soil stratigraphy, riverside drains, irrigation ditches, and domestic groundwater pumpage