Delineating surface water bodies for irrigation management: comparison of the NHD, manual, and LiDAR-based delineations

Abstract:

Surface water databases, such as the National Hydrography Database (NHD), are often developed at spatial resolutions that capture medium to large water bodies, those that would have the greatest impact on regional water budgets and management. However, small scale waterbodies often play a role in local hydrology and resource management, but they may not be present in national databases or land-use inventories. In the Mississippi River Alluvial Plain (i.e. the MS Delta), agricultural producers, stakeholders and resource managers are exploring options to utilize small man-made or natural water bodies for alternative irrigation sources during the agricultural growing season. Increasing surface water utilization for irrigation may help decrease pressures on groundwater sources, which have become depleted over the past several decades. However, there is a need for an accurate inventory of surface water sources and volumes to estimate their irrigation potential. In flat terrain, such as the MS Delta, the National Hydrography Database (NHD) falls short with representing surface water bodies. High resolution data, like LiDAR, may provide better resolution of water bodies and allow for correct representation of surface hydrology. In this study we compare the NHD with manually-delineated and LiDAR-generated lentic water bodies in three HUC-10 watersheds that overlap with areas of aquifer drawdown in the MS Delta: Harris Bayou (0803020703), Mound Bayou (0803020704), and Porters Bayou (0803020705). Using the Mound Bayou HUC 10 boundary as an example: the NHD delineated 77 water bodies with a total surface area of 2.06 km², while the LiDAR delineated 376 water bodies with a total 9.94 km² surface area. Manual delineations found 268 water bodies with 9.14 km² surface area. Average depths of water bodies are being collected through information from property owners, state agencies, LiDAR, and bathymetry. This information will be utilized to estimate volume and examine basic water budgets. This presentation will demonstrate how the database is being developed and provide an example of how this information can be used to identify locations for enhanced surface water use for irrigation.