Simple Model to Predict Irrigation Reservoir Water Qualities

Abstract

Usually irrigation reservoirs are shallow and closed water way systems of smaller volume of water compared with ponds or lakes. Irrigation reservoir water qualities in urban area are frequently affected by inflow of domestic wastewater containing higher concentration of TP and TN. Simple models are necessary to manage irrigation reservoir water qualities.
Vollenweider's type models for TP loading were examined to predict water qualities of 6 irrigation reservoirs in Nagoya City. The model applied for OECD's Inland Water Project on Shallow lakes and Reservoirs (1979),
[P]λ=[P]i·(1+7.239τ^0.608/Z^0.5)^-1,
provided satisfactory estimate of TP concentration. Since the ratio of predicted to observed TP concentrations is within the range of 1/1.5 to 1.5 for all irrigation reservoirs, this prediction model is adequate peculiar type of water like a very small and shallow.
Finally, the annual average concentration of TP gave good correlations to annual average concentrations of COD (γ=0.91), TN (γ=0.82) and Chl. a(γ=0.94), respectively, for 37 irrigation reservoirs in the city. These correlations support further application of the model for prediction of irrigation reservoir water qualities.