Comprehensive evaluation of agricultural waste and runoff management for water quality control: Completion report of a feasibility study and project proposal to the Inland Waters Directorate, Environment Canada
A literature review been carried out on the effects of agricultural practices on water quality of streams and waterways. The problem was broken into seven sections: soils and fertilizers, soils and pesticides, sediment loss and transport, animal wastes, hydrology of agricultural areas, rural sociology and modelling non-point water pollution. The transportation of polluting materials to the waterways is primarily through solution in the surface and ground water, and through adsorption on sediments which are transported to the waterways. The keys to predictions of such movements are the hydrologic model and sediment yield model. When the limits of these transporting mechanisms are determined for a given area, soil type and cropping system, then the inputs of pesticides, nutrients, (N and P) and organic material to these mechanisms may be estimated from known relationships available in the literature and from concurrent investigations. Movement of nitrates, water-soluble pesticides, herbicides and organic materials would be estimated from a hydrologic model, either through surface or shallow sub-surface water movement models. Movement of adsorbed phosphates, pesticides, herbicides and organic material would be from the sediment yield model and from the mineralogy and fertility level of the soils yielding the sediment. Exchange reactions of materials between solution and sediments as well as vapor movements remain to be evaluated. The probability of estimating these transporting mechanisms and thus the flow of pollutants, depends on accurate data on soil type, topography, fertilizer use, cropping systems, pesticide use, animal density etc. and on adequate knowledge of their interaction under defined climatic and management systems. A data file can be used with simulated peak-runoff steady state models to estimate pollutant movements under various land use systems. Relative responsiveness of communities to proposed changes can be estimated from socio-economic and educational levels, using several available scales. It would appear that enough information is available to warrant a first approximation at simulating the effects of agricultural practices and peoples attitudes on water quality in a defined agricultural watershed.