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EVALUATING HSPF IN AN ARID, URBANIZED WATERSHED (2005)

Ackerman, Drew ; Schiff, Kenneth C. ; Weisberg, Stephen B.

Oxford, UK : Blackwell Publishing Ltd

Journal of the American Water Resources Association 41 (2005), S. 0

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ISSN: 1752-1688

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Architecture, Civil Engineering, Surveying , Geography

Notes: : The Hydrologic Simulation Program-FORTRAN (HSPF) is a powerful time variable hydrologic model that has rarely been applied in arid environments. Here, the performance of HSPF in southern California was assessed, testing its ability to predict annual volume, daily average flow, and hourly flow. The model was parameterized with eight land use categories and physical watershed characteristics. It was calibrated using rainfall and measured flow over a five-year period in a predominantly undeveloped watershed and it was validated using a subsequent 4-year period. The process was repeated in a separate, predominantly urbanized watershed over the same time span. Annual volume predictions correlated well with measured flow in both the undeveloped and developed watersheds. Daily flow predictions correlated well with measured flow following rain events, but predictions were poor during extended dry weather periods in the developed watershed. This modeling difficulty during dry-weather periods reflects the large influence of, and the poor accounting in the model for, artificially introduced water from human activities, such as landscape overwatering, that can be important sources of water in urbanized arid environments. Hourly flow predictions mistimed peak flows, reflecting spatial and temporal heterogeneity of rainfall within the watershed. Model correlation increased considerably when predictions were averaged over longer time periods, reaching an asymptote after an 11-hour averaging window.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1752-1688.2005.tb03750.x

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A Regional Survey of the Microbiological Water Quality along the Shoreline of the Southern California Bight (2000)

Noble, Rachel T. ; Dorsey, John H. ; Leecaster, Molly ; [et al.]

Springer

Environmental monitoring and assessment 64 (2000), S. 435-447

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ISSN: 1573-2959

Keywords: regional survey ; water quality ; indicator bacteria ; total and fecal coliforms ; enterococci

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract A regional survey of the microbiological water quality along the shoreline of the Southern California Bight (SCB), from Point Conception south to Ensenada, Mexico, was conducted during August, 1998, by 36 agencies under the coordination of the Southern California Coastal Water Research Project (SCCWRP). Microbiological water quality was assessed by calculating the percentage of shoreline-mile-days that exceeded bacterial indicator thresholds for total and fecal coliforms, total/fecal ratios, and enterococci. Sample sites were selected using a stratified random sampling approach, with the SCB recreational shoreline divided into six strata: high- and low-use sandy beaches, high- and low-use rocky shoreline, and perennial and ephemeral freshwater outlets. Samples were collected on a weekly basis at a total of 253 sites, beginning on August 2nd, 1998 and continuing for five weeks. Samples were analyzed by 22 participating labs using their normal methods (multiple tube fermentation, membrane filtration, Colilert® and/or Enterolert®). All labs met testing criteria established through intercalibration exercises and quality control check samples distributed during the sampling period. Nearly 95% of the shoreline-mile days did not exceed daily and monthly bacterial indicator thresholds, demonstrating good bacteriological water quality along the SCB shoreline. Freshwater outlets, comprised mainly of storm drains, had the poorest water quality with 60% and 40% of the shoreline-miles exceeding monthly and daily thresholds, respectively. Freshwater outlets were also more likely to demonstrate exceedances by multiple indicators at a single site, and repeat exceedances at sites over the five-week period. Compared with the southern California beaches, Mexican beaches had nearly 5 times the number of exceedances for total and fecal coliforms, and nearly 8 times the number of exceedances for total/fecal ratios.