Water Quality Dynamics in Agricultural Ponds in Mississippi: In situ Measured Parameters

Abstract. The intensification of agricultural production in northwestern Mississippi over the past few decades has resulted in an increase in water withdrawals for irrigation and a dramatic decline in groundwater levels in the Mississippi River Valley Alluvial (MRVA) aquifer. Across the Mississippi Delta Region (MDR), groundwater is the primary and ultimate source of water for irrigation of crops when other surface water sources are absent or have been depleted. The MDR represents 93.7% of the total irrigated area in Mississippi, of which 97.4% withdraws groundwater from the MRVA aquifer at an average rate of roughly 530 m³yr^-1 for each hectare of cultivated land. The increased demand on groundwater is of special concern for regulatory agencies, the scientific community, and producers because such withdrawal rates exceed the annual recharge capacity of the aquifer. Multi-purpose best management practices (BMPs) as on-farm water storage (OFWS) systems have been implemented throughout the MDR in an attempt to reduce groundwater withdrawals, offer further sources for irrigation, improve water quality downstream, and promote water conservation. An OFWS system typically includes a tailwater recovery ditch that collects surface runoff and irrigation tailwater and an agricultural pond, or on-farm reservoir, to store surface water for later use. While ponds provide stored surface water for irrigation, there is a lack of field data to better understand the water quality of this source, and the implications of using this water on agriculture is scarce in the scientific literature. This study presents preliminary results of monitoring and analysis of in-situ water quality parameters measured in two agricultural ponds established in two farms located in Porter Bayou Watershed, Mississippi. Water supply from the investigated ponds is suitable for irrigation of crops although the preliminary results so far are for only three water quality parameters that are of central interest to irrigated agriculture.