Agriculture 



the Stream. Nineteen priority sites affected by animal waste were identified as part of the 

 208 Rural Runoff Inventory. 



Animal waste constituents cause turbidity and eutrophication, which in turn affect color, 

 taste, and odor, and increase the cost of treating the water for use as potable water supply. 

 Sediment, excess nutrients, and agricultural chemicals further escalate water supply 

 treatment costs. 



The agriculturally related resource problems of Aquidneck Island have been given 

 particular attention. Aquidneck Island was cited as the highest priority area in the state for 

 the reduction of agricultural non-point sources of pollution in the RI 208 Areawide Water 

 Quality Management Plan. Of the state's 53 highest priority watersheds identified during 

 the planning process, 13 were on Aquidneck Island, and of these, 7 were in the top 8. The 

 priority ranking of these watershed areas was based primarily on amount of sediment 

 delivered to waterbodies and potential waterbody use. 



In 1980, the Town of Middletown requested assistance under the Resource Conservation 

 and Development (RC&D) Program in solving the agricultural non-point source water 

 quality problems in its water supply watersheds. Although a Rural Clean Water Project 

 proposed for the island in 1981 was never funded, an SCS Watershed Protection Project 

 was initiated in 1984, sponsored by the Eastern Rhode Island Conservation District 

 (ERICD). 



Data collected during the SCS watershed planning investigations on Aquidneck Island 

 has revealed disturbing trends. Excessive sheet, rill, and ephemeral gully erosion on 

 cropland has caused reduction in crop yields due to erosion and sedimentation damage and 

 due to depletion of the soil resource base. Further, water quality in streams and in 7 

 municipal water supply reservoirs has been impaired as a result of sediment, phosphorus, 

 pesticide, and animal waste inputs from agricultural enterprises. 



A Cropland Erosion Study conducted from May 1984 to March 1985 by the ERICD 

 showed that the 2840 acres of Island cropland were losing a total of 25, 900 tons of soil 

 per year to sheet, rill, and ephemeral gully erosion. Although soils in the watershed have 

 been assigned a tolerable soil loss limit of 3 tons/acre/year, 33 percent of acreage was 

 eroding at up to twice the limit, 21 percent at 2-4 times the limit, and 27 percent at over 4 

 times the assigned limit. ERICD estimated that loss of soil depth would force abandonment 

 of 300 acres in the next 30 years, and an additional 720 acres in 60 years. 



ERICD found that erosion rates do not vary significantiy with crop type, but do vary 

 with slope. The economic value of nutrients lost, crop damage due to erosion, and loss of 

 soil productivity exceeds $200,000 annually in the watershed, with off-site sediment and 

 water quality problems costing an additional $20,000 per year. 



Total sediment yield to the stream system is estimated to exceed 11,700 tons per year, 

 with nearly 5300 tons of sediment deUvered to the reservoirs annually. Nutrients 

 associated with runoff and sediment have contributed to reservoir eutrophication, and 

 oxygen depletion. Lawton Valley reservoir experiences periods of hypoUmnetic anoxia. 

 The contaminant inputs also result in increased treatment cost, taste and odor problems, and 

 higher levels of trihalomethanes due to increased use of chlorine in treatment. 



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