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A Computational Model for the Determination of Optimal Seasonal Nitrate Loads on Farmlands

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Watershed Management to Meet Water Quality Standards and Emerging TMDL (Total Maximum Daily Load) Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005  701P0105.(doi:10.13031/2013.18131)
Authors:   V.O.S. Olunloyo, O. Ibidapo-Obe, and T. A. Fashanu

In many developing countries, agricultural production is the mainstay of the economy, and improved agricultural production usually means the proliferation of small to medium scale farming and widespread use of fertilizers. In cases like Nigeria, it has led to the establishment of a National Fertilizer Company. However, in view of the rudimentary level of infrastructure in rural areas, groundwater remains the only reliable source of water supply for domestic and other uses in the rural community. In such circumstances, heavy use of fertilizers poses a health threat to the community especially in cases where chemical treatment of domestic water supply is not available. The middle belt zone of Nigeria falls into such a category and our paper traces the historical use of Nitrates as fertilizer input over the last three decades. As a means of monitoring and assessing 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 establishment of TMDL for specified well depths for various categories of water use in such environment (e.g. domestic use, irrigation etc). Our computational scheme can also be generalized to handle other types of agricultural/industrial contaminants.

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