Managing conflicting water resources requirements in coastal wetlands: case study Pevensey Levels, UK

摘要

The Pevensey Levels is an area of reclaimed coastal wetlands located in East Sussex, UK. Agricultural and land-drainage activities dominate land use and have impacts on water quality within the Levels. The dense arterial ditch network which drains the levels suffers from nutrient enrichment, in particular orthophosphate PO_3~(4-) and inorganic nitrogen compounds (NH_4~+, NO_2~- and NO_3~-). The primary drivers behind the increase in nutrient concentrations are agricultural intensification, conversion to arable farming and point source pollution (particularly from two nearby Sewage Treatment Works). This study describes water quality data from January 1994 to July 2005 in order to discern temporal and spatial nutrient trends. It is evident that water quality within the Pevensey Levels is degraded. Concentrations of NH_4~+, NO_2~- and PO_3~(4-) throughout both major catchments are elevated, whilst concentrations of NO_3~-are lower than expected, indicating that many sites may also experience problems with low levels of dissolved oxygen. The Pevensey/Hurst Haven catchment was found to have significantly higher concentrations of all determinands, primarily as a result of effluent discharge from the Hailsham STWs. The Wallers Haven catchment was also found to experience water quality problems, but to a lesser extent. Over the period of observation, chemical P stripping was introduced at the Hailsham STWs, resulting in a significant decrease in recorded PO_3~(4-) concentrations. However, although external nutrient loading has decreased, water quality recovery limited. Suggestions are made for further research into the reasons for this lack of improvement.