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

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

Since the 1970’s, groundwater levels in the Mississippi Alluvial Aquifer have decreased as the number of irrigated acres in the Mississippi Delta has increased. Today, there are roughly 18,000 permitted irrigation wells dependent on water from the Mississippi Alluvial Aquifer, with approximately 50,000 new irrigated acres added both in 2011 and 2012. As concern has grown over groundwater declines and increasing fuel costs to run irrigation pumps, farmers have been implementing more irrigation conservation measures, such as on farm water storage (OFWS) systems. These systems began appearing in the Mississippi Delta in 2010 in conjunction with the implementation of the Mississippi River Basin Healthy Watersheds Initiative (MRBI). OFWS systems typically are surrounded by fields that are padded and piped, directing rainfall and runoff to a tailwater recovery ditch, from where it is then pumped into a pond for storage. Water is pumped from the pond and used for irrigation at a later date. These systems offer farmers the dual benefit of providing water for irrigation and also capturing nutrient rich tailwater for on farm reuse. This presentation will give an update on the project, which has monitored water savings and nutrient levels at two OFWS systems, one each at Metcalf Farm and at Pitts Farm, in the Porter Bayou Watershed, Mississippi. Data collection began in February 2012 and is ongoing, with water samples collected for analysis every three weeks throughout the growing season from March-October and every six weeks through the off season. Cumulative readings were also taken on flow meters to measure water use from the storage pond. The ability of these systems to reduce downstream nutrient concentrations has been mixed, with systems performing better when the tailwater recovery ditch is not full and can contain runoff on site. Thus, better management will improve the nutrient reduction potential of these systems. The water savings potential of these systems has been substantial. Metcalf Farm used 42 and 17 million gallons of water from the storage pond in 2012 and 2013, respectively; Pitts Farm used 60 and 56 million gallons of water from the storage pond in 2012 and 2013, respectively. These amounts reflect savings in groundwater that was not pumped from the Mississippi Alluvial Aquifer.

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