A Computational Method for Prescribing Seasonal Nitrate Loads on Farmlands to Preserve Underground Freshwater Resources

摘要

To date, widespread proliferation of nitrogen based manure in support of arable agricultural production has continued with little or no control. This trend is in spite of increase in medical pointers to the carcinogenic effects of excess nitrates in human systems. Small and large scale nitrate regulation policies on farmlands are fast evolving, especially in modern European agricultural communities. This is not true of many developing countries where agricultural production is the mainstay of the economy. Such economies are characterized with rudimentary level of infrastructure in rural areas. In such cases, scarcely treated groundwater remains the only reliable source of water supply for domestic and other uses. As a means of monitoring and regulating the risk to aquifers in this zone, a mathematical model is developed based on the Space-Time Conservation Element/Solution Element (CE/SE) numerical scheme for estimating the breakthrough curves of nitrate in aquifers in the neighborhood of farmlands. The model accommodates both the seasonal nature of fertilizer application as well as the stratification in geological log. Such curves enable the prescription of seasonal nitrate loads for specified well depths for various categories of water use in such environment (e.g. domestic use, irrigation etc). The developed computational scheme can be generalized to handle pastoral farming and other industrialuclear contaminants.