WATER-QUALITY IMPROVEMENT AT THE WATERSHED SCALE IN AN ANIMAL PRODUCTION AREA

Surface water quality is a problem in many animal production areas. Wa ter quality control at the watershed scale is emerging as a procedure to deal with point and nonpoint source pollution. The objectives of th is paper are to present the procedures for implementing best managemen t practices (BMP) in a 5.3 km(2) experimental watershed and to assess the effect of the BMPs on water quality. A monitoring station measured flowrate and water quality parameters at the outlet of the experiment al watershed and at that of a control watershed. The experimental setu p was such that the implementation of BMPs took place one-year after i nitiating the water quality monitoring program. Also, no changes in la nd use and fertilization practices occurred in the control watershed. From the data analyzed, 90% of the point source pollution came from le aking liquid manure tanks and from manure piles stored directly on the ground; corrective measures consisted in the construction of animal w aste tanks. Budgets of nutrients at the field scale showed that 63% of cultivated areas were in surplus of phosphorus compared to 42% for ni trogen. Fertilization plans included a change in timing and amount of manure applied. Water quality monitoring showed that the most problema tic parameters were phosphorus, fecal coliforms, and fecal streptococc i. Time series analyses showed a highly significant decrease in total phosphorus concentration and a significant decrease in fecal streptoco cci. No significant decrease in fecal coliforms was observed, probably because four out of six domestic sewage systems still discharged dire ctly into the watercourses at the end of the monitoring period. Water quality improvements were detected in the watershed following the impl ementation of BMPs over a period of 2.6 years.