RELATING WATER BUDGET AND GEOCHEMISTRY TO THE CONSERVATION AND PROTECTION OF A GROUNDWATER-DEPENDENT PRAIRIE WETLAND

Threats to water quality and quantity required by groundwater-dependent ecosystems relate mainly to hydrologic alterations in the groundwater capture zone. Because recharge zones often underlie a mosaic of owners, strategies for protection may be complex and difficult. Environmental concerns at the Pigeon Point Preserve in southeast North Dakota reflect a range of problems encountered in the protection of these ecosystems. The preserve comprises springs and seeps along the Sheyenne R, where the river cuts deeply though coarse fan deposits of glacial L Agassiz. The north-facing slope and discharge of mineralized groundwater creates a wetland that hosts unusual boreal species. Modeling and monitoring the water budget indicates that 0.2 cms of groundwater flows into the preserve, with roughly only 10% of the water recharged directly on the preserve’s 300 upland hectares. Long-term, steady-state discharge occurs through streams (33%), ET (44%), and groundwater lost to the river (23%). Water discharged from springs at increasing elevation reveal increasing mineralization and reducing conditions. Recharge for the higher elevation springs occurs through organic-rich wetlands 1.6 km from the seepage face, while water supplying the lower springs infiltrates in more distant stable sand dunes. Unregulated flowing wells completed in bedrock contribute salinity and boron to shallow groundwater. Potential and real threats to the ecological integrity of the springs are at least 6-fold: changing land cover, ag drainage, urban water supply, uncontrolled flowing wells, herbicides and invasive species, and climate change. In addition, remarkable changes in the Sheyenne R flow have occurred since 1993. Because of an 9.6-m rise in the lake, pumping of water out of the non-contributing Devils L basin began in 2005 and has increased to 7 cms. Improved ecological conditions of the riparian forest at Pigeon Pt may occur as a consequence of more floods.