The determination of total nitrogen and total phosphorus concentrations in freshwaters from land use, stock headage and population data: testing of a model for use in conservation and water quality management

1. Nutrient concentrations (particularly N and P) determine the extent to which water bodies are or may become eutrophic. Direct determination of nutrient content on a wide scale is labour intensive but the main sources of N and P are well known. This paper describes and tests an export coefficient model for prediction of total N and total P from: (i) land use, stock headage and human population; (ii) the export rates of N and P from these sources; and (iii) the river discharge. Such a model might be used to forecast the effects of changes in land use in the future and to hindcast past water quality to establish comparative or baseline states for the monitoring of change. 2. The model has been calibrated against observed data for 1988 and validated against sets of observed data for a sequence of earlier years in ten British catchments varying from uplands through rolling, fertile lowlands to the flat topography of East Anglia. 3. The model predicted total N and total P concentrations with high precision (95% of the variance in observed data explained). It has been used in two forms: the first on a specific catchment basis; the second for a larger natural region which contains the catchment with the assumption that all catchments within that region will be similar. Both models gave similar results with little loss of precision in the latter case. This implies that it will be possible to describe the overall pattern of nutrient export in the UK with only a fraction of the effort needed to carry out the calculations for each individual water body. 4. Comparison between land use, stock headage, population numbers and nutrient export for the ten catchments in the pre-war year of 1931, and for 1970 and 1988 show that there has been a substantial loss of rough grazing to fertilized temporary and permanent grasslands, an increase in the hectarage devoted to arable, consistent increases in the stocking of cattle and sheep and a marked movement of humans to these rural catchments. 5. All of these trends have increased the flows of nutrients with more than a doubling of both total N and total P loads during the period. On average in these rural catchments, stock wastes have been the greatest contributors to both N and P exports, with cultivation the next most important source of N and people of P. Ratios of N to P were high in 1931 and remain little changed so that, in these catchments, phosphorus continues to be the nutrient most likely to control algal crops in standing waters supplied by the rivers studied.

Proceedings of the Second American-Soviet Symposium on the Use of Mathematical Models to Optimize Water Quality Management, Bloomfield Hills, Michigan, USA, August 27-30, 1979 /

Mode of access: Internet.

Data base system for State water quality management information system /

Mode of access: Internet.

Water quality management program, supplemental guidance for FY 81

Cover title

Water quality management five year strategy, fy 81-baseline.

Jan. 1980.

Conservation districts and 208 water quality management ... /

Mode of access: Internet.

Irrigated agriculture and water quality management.

Mode of access: Internet.

Water quality management plan for the Lake Champlain Basin (10-00) /

Mode of access: Internet.

Legal and institutional approaches to water quality management planning and implementation /

Includes bibliographies.

Water quality management plan for the Wisconsin River basin /

"July 1975"

Feasibility of a systematic approach to water quality management in Illinois : annual report of stream/lake classification project /

Pbk.

Illinois' agricultural water quality management programs : a status report : conference proceedings of April 13, 1982 at Department of Agriculture Auditorium, State Fairgrounds, Springfield, Illinois.

"June 1982."

Main report, environmental, economic, and social assessment of the Statewide Water Quality Management Plan : 208 Water Quality Management Planning Program /

"Prepared for the Illinois Institute of Natural Resources and the Illinois Environmental Protection Agency"--Cover

Section 208 water quality management planning work plan and budget : summary.

Cover title: Water quality management planning.

State of Illinois Environmental Protection Agency 208 water quality management planning program.

Cover and spine title: Water quality management plan.