Extending irrigation reservoir histories for improved groundwater modeling and conjunctive water management in two Arkansas critical groundwater areas

Authors: SHULTS, DANIEL - Arkansas State University; Reba, Michele; NOWLIN, JOHN - Arkansas State University; Massey, Joseph; READ, QUINTIN - US Department Of Agriculture (USDA)

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2024
Publication Date: 1/25/2024
Citation: Shults, D., Reba, M.L., Nowlin, J., Massey, J., Read, Q. 2024. Extending irrigation reservoir histories for improved groundwater modeling and conjunctive water management in two Arkansas critical groundwater areas. Agricultural Water Management. 293(108678):1-9. https://doi.org/10.1016/j.agwat.2024.108678.
DOI: https://doi.org/10.1016/j.agwat.2024.108678

Interpretive Summary: Aquifer decline and rising pumping cost have forced producers to construct on-farm storage reservoirs. A need to improve existing groundwater models that include these systems is evident. This study extends our knowledge of on-farm storage reservoir construction from those established by a previous study that tracked reservoir construction between 1996 and 2015 backward an additional 20 years to 1976 using older multi-band satellite and aerial imagery. Reservoir construction was classified into five-year bins starting in 1976 and ending in 2015. Relationships between time and depth to groundwater, reservoir size, previous land use, and saturated aquifer thickness are described and contrasted in the two study areas across the 40-year study period. This information will allow for improved conjunctive water management and will be used by land managers and groundwater-surface water modelers.

Technical Abstract: Agricultural land managers in the Mississippi Alluvial Plain rely on the Mississippi River Valley Alluvial Aquifer for the majority of the water used for irrigation in the region. Pumping that outpaces recharge has resulted in significant cones of depression in the region, increasing pumping costs and forcing producers to use more surface water, often in the form of constructing on-farm storage reservoirs. At the same time, efforts are underway to improve groundwater models to run scenarios of conjunctive water management in the region. The improved models require accurate depiction of how the system is being managed including the use of on-farm storage reservoirs. This study extends our knowledge of on-farm storage reservoir construction from those established by a previous study that tracked reservoir construction between 1996 and 2015 backward an additional 20 years to 1976 using older multi-band satellite and aerial imagery. The study area covers portions of two Critical Groundwater Regions in eastern Arkansas. Reservoir construction was classified into five-year bins starting in 1976 and ending in 2015. Details of how older imagery was processed and analyzed are provided. Previously, nearly 50% of the on-farm storage reservoirs had unknown construction dates, this contribution resolved construction dates for 85% and 72% of the reservoirs in the two study areas. Relationships between time and depth to groundwater, reservoir size, previous land use, and saturated aquifer thickness are described and contrasted in the two study areas across the 40-year study period. Use of the information provided will help guide policy and resource allocation for future reservoir construction activities and help improve conjunctive water management of the region. Specifically, the addition of this historic information will allow modelers to further refine groundwater-surface water models and should improve water resources scenarios that include reservoirs as a tool to arrest or reduce groundwater decline.