Nitrate in groundwater; a water company perspective

More than 100 groundwater sources operated by Anglian Water Services are vulnerable to diffuse and point pollution, and 33 of these sources have nitrate concentrations in excess of 50 mg l (super -1) as NO (sub 3) . Most time series nitrate data "recess" to a long-term rising baseline, upon which seasonal variations and/or data scatter are superimposed. Investigations at boreholes abstracting from the Chalk Aquifer show that concentrations decrease with depth below the water table and with time after pump start-up. Abstraction rates do not affect concentrations but the combination of boreholes in use does. A reliable and robust semi-quantitative method for predicting future nitrate concentrations has been developed. Use of this method has allowed a rigorous definition of capital investment requirements under the AMP4 process to maintain compliance with drinking water standards. The method has been used to predict short-term nitrate concentrations for a variety of recharge scenarios.