Rezatec, the innovative landscape intelligence company, has been using it unique Earth Observation (EO) techniques to provide Portsmouth Water with detailed insights into potential sources of nitrate pollution in its catchment.

Rising nitrate levels in Groundwater have been a concern of Portsmouth Water for some years and the company has endeavoured to understand more about the sources of this pollution. On top of the rising trend, fluctuations in nitrate levels are often seen to be somewhat correlated to water table levels but it has been suspected that significant ‘spikes’ in nitrate levels at a few of its boreholes may be caused by overland flows terminating in the significant number of chalk pits and sinkholes that are found in a wide band crossing the area’s predominant chalk geology.

The Downs and Harbours Clean Water Partnership, a partnership between Portsmouth Water, the Environment Agency and Natural England’s Catchment Sensitive Farming (CSF) programme, which has been in operation since 2008, enlisted Rezatec to find out more about how the effects of agricultural landscape management could be affecting the both the sources of drinking water and the environment, particularly the protected habitats of Portsmouth, Langstone and Chichester Harbours.

The Partnership was not only interested in land management related to farming but also that related to equine use, e.g. horse paddocks, stable yards, and dung heaps, which can all produce varying localised sources of nitrate pollution. The latter was included, owing to the significant level of horse ownership in Downs & Harbours project/Portsmouth Water supply areas.

Rezatec looked at the Lovedean and Northbrook areas of Portsmouth Water’s catchment area and used Earth Observation techniques to provide data analysis of the likely overland flow of nitrates, as well as mapping general agricultural land use, including crops types, which can provide an indication on the amount of nutrients and pesticides that could be applied to the land and therefore have an impact on diffuse pollution.  Rezatec then mapped these potential sources along with overland flow paths and sinkholes that allow nitrate pollution to enter the groundwater.

The results are presented in an interactive, online geo-spatial portal with dynamic maps and analytical risk analyses presented as user-friendly graphics and animations that allow Portsmouth Water to visualise their catchment area in a completely different way. This complements existing modelling of nitrate in groundwater and surface water systems  by Amec Foster Wheeler, the environmental consultancy.

Rezatec can aid the work of catchment managers by identifying hotspots of potential agricultural and anthropogenic pollution, mapping these alongside the topographic and hydrological landscape features, particularly sink holes, and analysing all these parameters together to provide a dynamic risk assessment of the likelihood of diffuse pollution across the catchments. This knowledge can then be used as a decision support tool to help develop mitigation strategies for both the Downs and Harbours programme and Portsmouth Water, under its own developing Catchment Management strategy, and local farmers to reduce levels of nitrates in the catchment.

Alastair Stewart is the Project Manager of the Downs and Harbours Clean Water Partnership at Portsmouth Water. He commented: “Rezatec has taken an exciting and innovative approach that may greatly increase our understanding of the relationship between sources of diffuse pollution and the landscape and how this affects the quality of water in the area.”

Philip Briscoe, Marketing Director at Rezatec added: “At Rezatec we thrive on deriving new EO techniques to support water companies improve water quality and reduce operational costs associated with water treatment, ground surveys and compliance. The challenge that Alastair and his colleagues set us to identify sources of nitrate pollution and its interaction with the landscape really played to our skills and experience.”

Rezatec uses advanced, scalable techniques to offer what it has termed ‘landscape intelligence’, which takes large volumes of Earth Observation data and uses it to analyse environmental risk and changes in agricultural land use. Rezatec now works with five UK water companies, including Scottish Water, South West Water and Bristol Water, leading the market in supporting catchment and general water quality management by identifying potential threats to the water supply, in particular from different sources of diffuse pollution.

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