The role of lateral exchange in modulating the seaward flux of CNP

Lead Research Organisation: Lancaster University
Department Name: Lancaster Environment Centre

Abstract

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Planned Impact

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Description We instrumented six river sites with hydrological and hydrochemical monitoring equipment. The six sites cover a range of geological settings, allowing us to look at the influence of geology on the dynamics of water fluxes from land to river, and the impact of such transient behaviour on nutrient loading to streams. Our results have revealed a range of behaviours, including: highly dynamic variation in water fluxes at the groundwater-surface water interface due to root water uptake under baseflow conditions; transitional flow behaviour on a seasonal time scale as streams losing water to groundwater become groundwater fed; other transitional behaviour as streams disconnected from groundwater receive significant lateral flows as the local water table rises during periods of sustained precipitation. Our measurements of surface water chemistry indicate marked nutrient responses to these changing water fluxes. An example is enhanced transport of nitrate and dissolved organic carbon to our river reaches located on a sand and clay geology during periods of local water table rise contrasted with limited to no response in the chalk. Measurements of pore water chemistry in the banks and river bed taken every two months have enabled us to link chemical and water fluxes through the local near-stream environment. We have established clear links between surface water chemistry and baseflow index, as originally proposed. We believe that this will allow a generalisation of our findings to a wide range of environments.
Exploitation Route The findings to date have potential value to environmental regulators and river managers, through an improved understanding of the dynamic nature of water and solute fluxes at the groundwater - surface water interface, and the impact of these of nutrient loading in surface waters.
Sectors Environment
 
Description Our work has established a clear link between macronutrient behviour in surface waters and baseflow index, which we believe will have broader generalisation for water resource managers.
First Year Of Impact 2015
Sector Environment
Impact Types Policy & public services