A system dynamics model of El Paso County Water Improvement District No.1

The Paso del Norte Region is a desert area with limited surface and underground water resources. El Paso County Water Improvement District No. 1 (EPCWID#1) plans to implement strategies that save water and reduce salinity. An irrigation computer model of EPCWID#1 was created using STELLARTM software. Input data for the model was analyzed using statistical analysis functions in EXCELLRTM. The model identifies management options for more efficient water allocation and salinity damage reduction. This research includes collection and analysis of available data for water flows and total dissolved solids (TDS) from 1997 to 1999, and the identification of information gaps in the system. Regression equations were obtained to control the model. A comparison of model results with actual data shows good approximation. Also, a comparison of model results with results from a previous research made by Miyamoto et al, gives validation to the model. The irrigation system computer model was divided in thirteen sectors to facilitate model understanding. Three modeling scenarios (high flow year, low flow year, and severe drought year) were run to obtain the annual flow and salt load balances for the EPCWID#1. The model was used to calculate TDS concentrations in the three main canals inside the EPCWID#1 and to calculate the number of days with unsuitable water quality (TDS > 1900 mg/l). For both low flow scenarios, the Riverside Canal, which receives treated wastewater discharges from El Paso's wastewater treatment facilities, had the highest salinity and the highest number of days with unsuitable water quality.