HR: 1340h
AN: H33D-1410    [Abstracts]
TI: The Effects of Wetland Management on Nutrient Concentrations and Loads at Lower Klamath National Wildlife Refuge
AU: * Mayer, T
EM: tim_mayer@fws.gov
AF: US Fish and Wildlife Service, 911 NE 11th Ave , Portland, OR 97232-4181 United States
AB: Insufficient water supply and poor water quality are major problems in the Klamath Basin of southern Oregon and northern California, USA. Various land-management practices and competing demands for water in the basin have led to degraded environmental conditions and poor water quality (excessive nutrients, warm temperatures, high pH, low dissolved oxygen). One such land-management practice that has come under increased scrutiny is wetland management on the Lower Klamath National Wildlife Refuge. Wetlands on the refuge are intensely managed through a system of canals, drains, and water-control structures. They can be managed as permanently-flooded wetlands, seasonally-flooded wetlands, or farmed wetland units. The water quality impacts of this management are unknown. For this study, data on water-use requirements, field water-quality parameters, and nutrient (N and P) concentrations were used to develop water budgets and nutrient loads for the refuge. With respect to nutrients, the results showed that outflow nutrient concentrations at the refuge are generally greater than inflow concentrations, but outflow nutrient loads are reduced. From 55 to 77% of the mass of N and 19 to 51% of the mass of P entering the refuge wetlands is retained. Seasonal wetlands retain less P than permanent wetlands or farmed units, possibly because of the annual drying cycle, the later drainage dates, and predominance of annual vegetation. For all of the refuge wetlands, dissolved inorganic N is retained more efficiently than particulate organic N, and particulate P is retained more efficiently than soluble reactive P. The reasons for these findings will be discussed. The ultimate effect of refuge wetland management is to decrease net N and P loads but increase the ratio of bioavailable P to bioavailable N in the refuge outflow.
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0496 Water quality
DE: 1806 Chemistry of fresh water
DE: 1890 Wetlands (0497)
SC: Hydrology [H]
MN: Fall Meeting 2005