Watershed and lake water quality assessment: An integrated modeling approach

K. R. Mankin, J. K. Koelliker, P. K. Kalita

Research output: Contribution to journalArticlepeer-review


Watershed planning groups and action agencies seek to understand how lake water quality responds to changes in watershed management. This study developed and demonstrated the applicability of an integrated modeling approach for providing this information. An integrated model linking watershed conditions to water-quality of the receiving lake incorporated the following components: (1) an event-based AGNPS model to estimate watershed pollutant losses; (2) annualization of AGNPS results to produce annual lake pollutant loadings; (3) a baseflow separation package, SAM, to estimate baseflow; (4) estimates of nutrients in baseflow and point sources; and (5) linkage of watershed loadings directly to EUTROMOD lake water quality algorithms. Results are presented for Melvern Lake, a 28-km2 multipurpose reservoir with a 900-km2 agricultural watershed in east central Kansas. Reasonable estimates of current lake quality were attained using an average phosphorus availability factor of 31 percent to calibrate model results to measured in-lake phosphorus. Comparison of a range of possible scenarios, including all cropland changed to no-till (best case) and all CRP and good-condition grasslands changed to cropland (worst case), indicated only a (4 percent change for in-lake phosphorus and a (2 percent change for chlorophyll a. These results indicated that this watershed is not sensitive to projected changes in land use and management.

Original languageEnglish (US)
Pages (from-to)1069-1080
Number of pages12
JournalJournal of the American Water Resources Association
Issue number5
StatePublished - Oct 1999
Externally publishedYes


  • Agricultural hydrology
  • Modeling
  • Nonpoint source pollution
  • Water quality

ASJC Scopus subject areas

  • Ecology
  • Water Science and Technology
  • Earth-Surface Processes


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