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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #324084

Title: Impacts of forest to urban land conversion and ENSO phase on water quality of a public water supply reservoir

item Elias, Emile
item RODIGUEZ, ANTONIO - Tetra Tech
item SRIVASTAVA, PUNEET - Auburn University
item DOUGHERTY, MARK - Auburn University
item James, Darren
item SMITH, RYANN - New Mexico State University

Submitted to: Forests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2016
Publication Date: 1/27/2016
Publication URL:
Citation: Elias, E.H., Rodiguez, A., Srivastava, P., Dougherty, M., James, D.K., Smith, R. 2016. Impacts of forest to urban land conversion and ENSO phase on water quality of a public water supply reservoir. Forests. 7, 29.

Interpretive Summary: Both climate change and land use change affect water quality of the drinking water reservoir supplying the population of the City of Mobile, Alabama. We used two computer simulation models to evaluate the impact of watershed land use change on reservoir nutrients and total organic carbon. We found that urbanization increases all nutrient concentrations and TOC. This will increase the need for drinking water treatment to comply with the safe drinking water act. While there were higher nutrient concentrations during times of higher streamflow, these concentrations did not coencide with increased TOC, suggesting a delay in response, likely related to algae growth. In fact, the reduced flushing associated with La Nina events was weekly correlated with TOC indicating that lower flows may allow for increased algae growth and TOC concentrations.

Technical Abstract: We used coupled watershed and reservoir models to evaluate the impacts of deforestation and ENSO phase on drinking water quality. Source water total organic carbon (TOC) is especially important due to the potential for production of carcinogenic disinfection byproducts (DBPs). The Environmental Fluid Dynamics Code (EFDC) reservoir model is used to evaluate the difference between daily pre- and post- urbanization nutrients and TOC concentration. Post-disturbance (future) reservoir TN, TP, TOC and chlorophyll-a concentrations were found to be higher than pre-urbanization (base) concentrations (p<0.05). Predicted future median TOC concentration was 1.1 mg L-1 (41% higher than base TOC concentration) at the source water intake. Simulations show that prior to urbanization, additional water treatment was necessary on 47% of the days between May and October. However, following simulated urbanization, additional drinking water treatment might be continuously necessary between May and October. One of six ENSO indices is weakly negatively correlated with the measured reservoir TOC indicating there may be higher TOC concentrations in times of lower streamflow (La Niña). There is a positive significant correlation between simulated TN and TP concentrations with ENSO suggesting higher concentrations during El Niño.