Nutrient Reduction Benefits of On-Farm Water Storage Systems in Porter Bayou Watershed

Author(s): Tagert, M.; Paz, J.; Pote, J.; McCraven, K.; Kirmeyer, R.

The Mississippi River Basin contains over 60% of the harvested cropland in the United States, and the Mississippi and Atchafalaya Rivers contribute more than three-fourths of the total nutrient load to the Gulf. Since the 1970's, groundwater levels in the Mississippi Alluvial Aquifer have decreased at a rate of approximately 100,000 acre-feet per year due to increased irrigated acres. Today, there are roughly 18,000 permitted irrigation wells dependent on water from the Mississippi Alluvial Aquifer, with an average addition of approximately 35,000 new irrigated acres per year for the past few years. Adequate supply of good quality water is important to sustaining agriculture, the primary industry in the economically depressed Mississippi Delta. Due to concerns over groundwater declines and increasing fuel costs to run irrigation pumps, farmers have begun implementing irrigation conservation measures, such as creating on farm storage areas to capture irrigation and surface water runoff from the field for later use. These systems offer farmers the dual benefit of providing water for irrigation and also capturing nutrient rich tailwater for on farm reuse. This project includes monitoring of two on farm water storage areas in the Porter Bayou Watershed, Mississippi and has two primary research objectives: a) determine the downstream nitrogen and phosphorous concentrations of effluent from water storage systems and b) quantify the effects of water storage systems on downstream flow levels through a watershed. Data collection began in February 2012, with water samples collected for analysis every three weeks throughout the growing season from March-October. Effluent nitrate and phosphorus levels were significantly lower than the inlet levels at both on farm storage systems.

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