HUMAN AND HYDROLOGIC INFLUENCES ON UNIQUE PLAYA WETLANDS

A vast majority (~90%) of central Nebraska’s Rainwater Basin (RWB) wetlands have been lost due to conversion and degradation predominantly by modern agricultural practices. Efforts to maintain and restore these endangered wetlands are critical for protecting the millions of migratory birds that rely on them. These ephemeral, rain-fed playa wetlands are threatened by invasive species, climate change, drainage, reduced surface water inputs, and culturally-accelerated sediment inputs by recent surrounding human activity. Restoration via sediment excavation is one method for reducing the impact of excess sediment and invasive plant species on wetland habitat. The impact of excavation on RWB wetland hydrology is a subject of interest for land managers. This project seeks to evaluate the influence of natural predictor variables (rainfall, soil series, etc.) as well as human activities on wetland ponding in order to provide insight on what factors play the biggest role in determining ponding extent. Examples of influential human activities include land use type within the watershed, groundwater pumping into wetlands by land managers to induce ponding, presence of and filling of nearby irrigation pits, and sediment excavation for restoration. 16 years of Annual Habitat Survey data (2004 and 2006 to 2020) from the Rainwater Basin Joint Venture were used to determine previous ponding area in 35 of the Nebraska Game and Parks Commission’s Wildlife Management Areas which contain RWB wetlands. The Annual Habitat Surveys provide a yearly snapshot of the extent of functional and ponded wetland area in the RWB region during early spring. A classification and regression tree (CART) analysis can determine the relative influence of several fixed and dynamic factors that affect the extent of ponding area. This project utilizes data on wetland excavation for restoration purposes in 35 wetlands provided by the Nebraska Game and Parks Commission in order to evaluate the strength of influence of various excavation factors (excavation year, depth, amount of material removed, etc.) on ponding. Annual groundwater pumping records will also be provided by the Nebraska Game and Parks Commission to include in the analysis.