Catchment Dynamics

Central to the prediction of hydrological risks is the understanding of how water moves through catchments and how the rainfall input signals are filtered by the landscape. Science’s grasp on these issues is still weak and new forms of data and insight are challenging our current understanding. In order to make accurate predictions about how catchment may operate in the future, it is essential to understand how they are operating today.

My research has focused on both temperate and semi-arid environments and has aimed to address questions centred on how water moves through the catchment and how the system will respond to external forcing. The movement of water through the catchment has been approached through the concept of hydrological connectivity. Hydrological connectivity defines the probability that a point in the landscape will be able to transmit water to the catchment outlet. The external forcing issues have focused on the potential impacts of land use and climate change. I have addressed these issues have been addressed through a combination of data analysis and environmental simulation modelling.

Climate Change Impacts

The greatest hydrological risk facing global society this century will be the impacts of projected climate change. The potential impacts on agriculture, ecology and society will be filtered and delivered through the hydrological system. Therefore, to understand the potential impacts on society, it is essential to understand how the hydrological system may respond. This work is being undertaken using the CRUM3 distributed catchment simulation model. The modelling work is considering the uncertainty in the river flow predictions resulting from different regional climate models, the stochastic downscaling of the weather time series and from the model parameter set uncertainty. These different uncertainty sources are combined together with a statistical framework to give a probabilistic view of the magnitude of the projected changes. The understanding of the magnitude and probability of the changes enables effective management and mitigation of the water related issues.

Diffuse Pollution

Diffuse pollution from agriculture has the capability to impact the water quality and ecology of rivers and streams. My work has focused on the movement of fine sediment, nitrogen and phosphorus within the SCIMAP risk based framework. The SCIMAP framework aim is to determine the locations within the landscape that have the greatest risk of exporting nutrients or fine sediment to the river channels. These predictions are calculated through the joint consideration of the amount of material that could be exported and the probability of that material reaching the channel through an analysis of the hydrological connectivity. The SCIMAP approach has been applied to 12 locations within England and Wales as part of the Environment Agency / DEFRA’s Catchment Sensitive Farming Program.

Environment Modelling

The approach that I take to the investigation of hydrological and geochemical problems is centred within simulation modelling techniques. I have developed a series of models to address different problems which include the CRUM models (CRUM2D and CRUM3), the hydroAgent flow tracing technique and the CAS-Hydro model for the UK Water industry. The main model that I have developed and written is CRUM3. This model is a physically based, spatially distributed simulator of landscape scale hydrological. The model simulates the movement of water through the combined hillslope and river channel system. The model is currently being used to investigate the projected impacts of climate change on catchment behaviour and the hydrological connectivity dynamics of small catchments. CAS-Hydro is a landscape hydrological model and is also capable of simulating the movement of pollutants and nitrogen cycling. This model has been used for research for the UK Water Industry, Environment Agency and various research projects. More details. I have also developed a novel agent based simulation technique to trace the flows of water through the simulated catchment. This technique allows a powerful insight into how the model is predicting the movement of water through the catchment. Read more about my environment modelling, CRUM models, hydroAgents and CAS-Hydro.