Modeling riparian groundwater depth as a function of river flow for the Rio Grande at Albuquerque, NM

Riparian corridor ecological health is strongly tied to river streamflow. As climate change threatens to significantly reduce monthly streamflows in semi-arid regions, riparian groundwater will be similarly reduced, impacting native and non-native flora. This paper presents a geographic information system (GIS) based approach for creating comprehensive riparian water surfaces from point surface water and groundwater measurements. These water surfaces are used to calculate depth to groundwater as a function of river discharge for the study reach in Albuquerque, NM, USA. A one dimensional hydraulic model, calibrated with USGS streamflow data, was used to interpolate streamflow measurements throughout the study reach and provide the river water surface elevation for the entire river. The limitations of streamflow measurements in sand bed rivers are presented along with guidance on using stage-discharge curve data to calibrate hydraulic models. A GIS model that combines groundwater measurements and interpolated river water surfaces to produce comprehensive water surfaces for the entire riparian corridor is presented. Groundwater gradient from the river is calculated to interpolate the riparian water surface between well sites. For the study reach, the groundwater gradient is determined to be approximately linear on each side of the river and primarily controlled by urban groundwater pumping. Depth to groundwater is calculated by subtracting the water surface from the terrain. The impact of river discharge on depth to groundwater is analyzed. The reduction in depth to groundwater for a given discharge on the falling side of the hydrograph versus the rising side of the hydrograph is quantified. Native and non-native riparian species have different tolerances for groundwater depth: the impact of different flow rates on the ability of species to survive is presented. The depth to groundwater grids as a function of discharge provide a baseline model that can be used to predict climate change altered depth to groundwater. Future reductions in streamflow are correlated to new depth to groundwater grids. Although the model and analysis are demonstrated for the study reach, the approach may be utilized for any river system with a similar dataset available