Article Review: CEDAR CREEK

Debele, B., Srinivasan, R., and Parlange, J. Y. (2008). "Coupling upland watershed and downstream waterbody hydrodynamic and water quality models (SWAT and CE-QUAL-W2) for better water resources management in complex river basins." Environmental Modeling and Assessment, 13(1), 135-153.

The article presents a modeling framework of water quantity and quality of upland watershed and a downstream reservoir. Two models have been coupled: SWAT (Soil & Water Assessment Tool) and CE-QUAL-W2. SWAT is a hydrological and hydraulic 1-D hydrodynamic and water quality model used to simulate upland watershed and narrower streams. CE-QUAL-W2 is a waterbody laterally averaged (2-D) hydrodynamic model, suited for narrow and deep waterbodies where lateral variation is minimum. This modeling approach has been tested in Cedar Creek watershed, Texas. The main land uses is agriculture, forest and urban areas. The watershed is drained by two main creeks (Cedar and Kings) and seven smaller tributaries which feed into the Cedar Creek Reservoir. The mean depth of the reservoir is 6.5 meters, a surface area of 34,300 acres and a volume of 566,000 acre-feet. About 25 % of total reservoir inflow is lost through evaporation and approximately 10 % is withdrawn for urban consumption (Fort Worth and nearby towns). Data from a period of 5 years, from 1997 to 2001, was used to calibrate the models. The calibration of the reservoir hydrodynamic showed good waterbalance match between the observed data and simulated results. The water quality calibration was performed with first temperature followed by Dissolved Oxygen. A second dataset of water quality parameters such as organic nitrogen, organic phosphorus, phosphate, chlorophyll a, total nitrogen, and total phosphorus concentration, were available and used in the calibration. Comparison among observed and simulated water quality parameters showed reasonable agreements. It was concluded that this framework can properly simulate seasonal and intraseasonal distributions of many water quality variables, with exception of Chl-a, TP, TN and NH3/NH4. The reasons for that could be by low quality of these input dataset and error propagation and compounding. In conclusion, the authors state that the integration of such models of spatially variable upland watershed hydrological and water quality models with downstream waterbody hydrodynamic and water quality models can help the water resources management, allowing the backtrack of the spatial sources of contaminants and support a good decision making for water quality standards in downstream waterbody.