A Pilot Study for Water Storage and Carbon Variability in an Irrigation Pond of the Southeastern Plains, USA

Farm ponds are a common feature of agricultural landscapes for irrigation of crops. Yet small water bodies have been ignored as reservoirs and carbon balance features despite their ubiquity in the global landscape. These ponds contain surface water from precipitation and runoff, but in South Georgia, USA, groundwater supplementation is required to maintain a supply for irrigation. Key characteristics of these ponds, such as capacity and dynamics describing fluxes in quantity and quality, are not well known. In this area, irrigation ponds supplemented by groundwater have water quality issues that affect producers. In a pilot study to address this knowledge gap, storage dynamics and water quality, that is, dissolved organic carbon (DOC), were characterized from measurements of a regionally typical irrigation pond in 2022. Field surveys of pond depth and terrain were fused to create a topobathymetric elevation model of the pond and its environs. The pond has a volume of 5.06 +/- 0.29 ha-m that was used for irrigation during the growing season and was mostly replaced with groundwater. Concentrations of DOC ranged from 1.77 to 19.9 mg/L. Dissolved organic matter (DOM) indices reveal a shift from terrestrial-derived DOM earlier in the year to more microbial-derived DOM later. Together this integrated analysis of an irrigation pond in South Georgia analyzes water inflows and outflows, quantifies DOC, characterizes DOM, and models pond storage volumes.