Streamflow Output Research Articles

Nutrient Budgets for Agricultural Watersheds in the Southeastern Coastal Plain

Watershed—level agroecosystem studies are essential to relate land management to the external environmental effects produced by agricultural nutrients and to enhance our understanding of agricultural nutrient cycles. Inputs and outputs of N, P, K. Ca, Mg, and Cl were determined for four subwatersheds of the Little River in the Georgia Coastal Plain from 1979 through 1981. The four watersheds had 40, 36, 54, and 50%, respectively, of their land in agricultural uses (row crop and pasture). Prescipitation inputs and streamflow outputs were determined by field sampling of water volumes and nutrient concentrations. Agronomic inputs (from fertilizer and symbiotic N—fixation) and outputs in harvested material were estimated from land use data; countrywide averages of fertilizer applications and crop yield, and plot studies on peanuts and soybeans. All elements except Cl had greater inputs than outputs on each watershed each year. The general order of streamflow loads was Cl > Ca > K > Mg> N > P. Fertilizer inputs exceeded precipitation inputs for all elements on all watersheds. Outputs on N, P, and K in harvest generally exceeded streamflow loads, but harvest outputs of Ca, Mg, and Cl were generally lower than streamflow loads. The two watersheds with more agricultural land had consistently higher loads of N, K, Ca, Mg, and Cl in streamflow and had No3—N loads 1.5 to 4.4 times higher than loads from the less agricultural watersheds. Streamflow loads on the Little River watersheds were similar to those on other Coastal Plain agricultural watersheds with comparable land use and discharge volumes. Budgets for the upland portion of one of the watersheds indicated that large amounts of N, P, K, Ca, and Mg were not accounted for. about 56 kg°ha—1@?yr—1 of N were retained or lost to gaseous emissions from the uplands. Apparently, a large percentage of the nutrients applied to these watersheds was being retained somewhere in the watershed or being lost in some unquantified way.

Short term fluctuations in dissolved organic matter concentrations in streamflow draining a forested watershed and their relation to the catchment budget

AbstractDissolved organic matter (DOM) concentrations in throughfall, throughflow, and runoff were recorded in a small (95 ha) woodland catchment in North Warwickshire for a period of eight weeks following a prolonged dry spell. DOM is shown to be positively related to stream discharge over the sampling period, although distinctive flushing effects were identified. The net contribution of DOM to total dissolved solids load carried in the river was only 2.4 per cent, and represented significantly less than published carbon losses by mineralization of soil organic matter. Throughfall inputs were some 100 times higher than streamflow outputs from the catchment.

Catchment nutrient budgets and geological weathering in Eucalyptus regnans ecosystems in Victoria

The movement of water and nutrients (N, P, K, Na, Mg, and Ca) through Eucalyptus regnans dominated catchments in the Maroondah catchment near Melbourne were determined. Nutrient fluxes in precipitation and streamflow are discussed and used to prepare simple precipitation input – stream flow output catchment budgets. These budgets are similar to those found elsewhere in Australia and overseas with the exception of nitrogen. This was probably due to errors in measurement and incomplete quantification of nitrogen fluxes. Catchment sodium budgets were used to estimate geological weathering rates by two different methods. Both methods yielded similar results. Data from two other studies in Victorian forested catchments yielded results similar to those obtained from Maroondah. It was concluded that the bedrock weathering rate at Maroondah was approximately 700 kg ha-1 year-1 which is very similar to that found elsewhere. Nutrient inputs from geological weathering were then estimated and possible errors discussed.

Regression Analysis of Nonlinear Catchment Systems

The catchment is considered as a nonlinear system with rainfall input and streamflow output. The system is analyzed by using a discrete form of the nonlinear convolution integrals in conjunction with stepwise multiple regression to obtain a prediction equation from the available rainfall and streamflow records. Experimental results for two rural catchments show that the analytical techniques employed have practical application in the continuous simulation of complex catchment behavior.