HYDROGRAPH SEPARATION USING CHEMICAL TECHNIQUES - AN APPLICATION TO CATCHMENTS IN MID-WALES

A chemical technique is used to provide hydrograph separation for streams in the Llyn Brianne area of Mid-Wales. The technique uses mixing relationships for a conservative component, the acid neutralization capacity (ANC). A relationship is established between pH and ANC using the chemical analyses for 'spot' samples and with this the ANC is calculated from continuous pH measurements. The technique separates the hydrograph into soil waters and deeper waters. A comparison of the effects of land-use differences is made. The results suggest that changes in both soil chemistry and hydrological pathways may result from afforestation. Long-term modelling work may benefit from a combined approach in which mixing-model results are used to allow predictions of short-term stream chemistry changes. © 1990.