Statistical Analysis of Flow Exchange and Salt Loading between the Rio Grande and Underlying Aquifers

This paper provides statistical analysis of flow exchange and salt loading between the Rio Grande and underlying aquifers for the Rio Grande Project Area, extending from Caballo Reservoir in New Mexico, continuing through the urbanized areas of Las Cruces, New Mexico and El Paso, Texas to Fort Quitman, Texas. The authors analyzed the river flow, TDS and salt loading at selected three segments of the river reach and associated underlying aquifers. The total salt loading within each segment was computed to determine exchange of salt loading between the river and underlying aquifers. The salt concentrations continue to increase downstream, up to 3,200 mg/L on average at Fort Quitman during irrigation season, approximately five times higher than the water TDS released from the Caballo Reservoir. This is due to the river collecting irrigation return flows, municipal wastewater discharge and natural discharge of saline groundwater. Salt exchange patterns between the river and underlying aquifers were also identified.