Modeling salinity control alternatives for the Rio Grande Project
The Rio Grande Compact established a formal and legal framework for addressing water allocation issues associated with the in the Rio Grande Project; but, the compact did not address salinity issues. Therefore, upstream farmers have no incentive to consider the economic impacts that salinity inflict on others. Downstream salinity is generated principally by upstream agricultural activities. Downstream irrigation and municipal water users are impacted by salinity. Water policies can be designed to reduce salinity considering impacts on agricultural profits. This study evaluates the economic impacts on agricultural profits of six salinity control alternatives for the Rio Grande Project. These alternatives are no control, land retirement, irrigation water price, water allocation adjustments, water allocation based on economic efficiency, and canal lining. A salt balance analysis was first conducted to investigate salt trends, salt flow, and/or salt accumulation in the region. Second, agricultural production functions were estimated. Third, salinity control alternatives were evaluated within a regional optimization model (RGP) to determine the effect of changes in salinity on agricultural users. The RGP model included agricultural benefits, water and land availability, and water quality constraints. The model estimated river water quality, crop patterns, and cost of salinity control alternatives that maximized agricultural benefits. Then, a benefit cost analysis was developed to select the cost effective alternative. The annual salt flow passing between gage stations from San Marcial (New Mexico) to Fort Quitman (Texas) seemed to be invariable. While downstream salinity concentration increases as irrigation deliveries reduce water flow in the river, indicating that salinity policies for the Rio Grande Project should address salinity concentration and not salt load. The RGP results showed that the downstream regional profits may be increased by reducing downstream salinity concentration as TDS. Downstream farmers respond by substituting less profitable crops for economically more profitable crops. The proposed salinity control policies contribute differently to regional agricultural profits because each alternative differs in its effects on water allocation, land use, and water quality. The estimated benefit-cost ratio for salinity control using water allocation based on adjustment and economic efficiency are greater than estimated ratios for the other alternatives, but the feasibility of a alternative not only depend of the economic variables but also on other legal and political factors. The economic, political, legal implications of a canal lining scenario are less significant than the estimated for other alternatives. Therefore, the lining of canal systems in the Rio Grande Project is considered the preferred alternative to improve water quality for downstream users in the Rio Grande Project, with a direct benefit of $2 per $1 of estimated cost.
Environmental engineering|Agricultural economics|Civil engineering
Olaya, Mauricio, "Modeling salinity control alternatives for the Rio Grande Project" (2004). ETD Collection for University of Texas, El Paso. AAI3138515.