River Obstructions

Location of manmade barriers, mostly weirs, and natural features, such as waterfalls, on river courses in England and Wales. This dataset is known as "Potential Sites of Hydropower Opportunity" and has been created under the EA project "Opportunity and environmental sensitivity mapping for hydropower in England and Wales". The dataset shows the location of opportunities for hydropower and the basic environmental sensitivity, which considers the presence of fish species and whether the site has been designated as Special Area of Conservation (SAC), associated with exploiting them. Besides their location, the dataset includes information on river level height, up and downstream the barrier.


Study area

Provenance & quality

All the barriers were identified and mapped from OS MasterMap data, using the Digital River Network as reference. Head and flow values were used to generate potential power outputs expressed in terms of total capacity. Where available, Lidar data (vertical accuracy of 25 cm) was used to calculate the barrier height (head); otherwise, SAR data (vertical accuracy of 100 cm) was used. A number of data sources were used to estimate flow such as EA's Water Resources GIS database and flow data from gauging stations across England and Wales. The flow available at each particular barrier was calculated as the average flow (Qmean) minus the flow that is exceeded 95 % of the time (Q95). The environmental sensitivity associated with exploiting each barrier was assessed using EA compiled Fish Classification Schema data from the Water Framework Directive and Special Area of Conservation location dataset.

Correspondence/contact details


Spatial representation type
Spatial reference system
OSGB 1936 / British National Grid


Topic categories
Inland Waters
Geospatial / Map National River Flow and Networks