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LowFlows science

The requirement

Whether you need to estimate water resources for abstraction/discharge consents, environmental impact statements or hydropower potential assessment, LowFlows meets this challenge. It integrates within a GIS framework the latest hydrological models for predicting natural and artificially influenced river-flows within UK ungauged catchments.

LowFlows is widely used by the Environment Agency (EA) within the Resource Assessment Methodology and associated development of Catchment Management Abstraction Strategies (Holmes et al 2005). It is also used by the Scottish Environment Protection Agency (SEPA) in the implementation of the Controlled Activity Regulations.

Hydrological models within LowFlows

The main hydrological models within LowFlows (Young et al 2003 ) were originally developed by CEH in collaboration with the EA and SEPA.

These models allow you to estimate:

• Annual mean flow – estimated using a deterministic model calibrated on observed flow data from over 500 UK gauged catchments (Holmes et al 2002a).
• Annual flow duration statistics – modelled using a 'region of influence’ (ROI) approach to hydrological regionalisation (Holmes et al 2002b). Dimensionless gauged flow duration statistics from 'similar' catchments are combined to estimate statistics for the ungauged catchment which are rescaled by mean flow.
• Monthly mean flow –uses a similar ROI approach to estimate the proportion of annual runoff distributed over each month (Holmes et al 2002c).
• Monthly flow duration statistics –derived from dimensionless gauged monthly FDCs using the same procedure as the annual FDC model (Holmes et al 2002c).
• User-defined seasonal flow duration statistics - derived from dimensionless gauged monthly FDCs (Holmes et al 2002c).
• Base Flow Index - calculated for the ungauged site using the Hydrology of Soil Types (HOST) hydrological classification for the UK (Boorman et al 1995).

The process for deriving an annual flow duration curve is illustrated below.

LowFlows methodology for deriving an annual flow duration curve
within England and Wales

LowFlows Bibliography

Boorman DB, Hollist JM and Lilly A. (1995)
Hydrology of soil types: a hydrologically-based classification of the soils of the United Kingdom Institute of Hydrology Report No. 126.

Holmes MGR, Young AR, Gustard AG and Grew R (2002a)
A new approach to estimating Mean Flow in the United Kingdom. Hydrology and Earth System Sciences 6 (4) 709-720.

Holmes MGR, Young AR, Gustard AG and Grew R (2002b)
A Region of Influence approach to predicting Flow Duration Curves within ungauged catchments. Hydrology and Earth System Sciences 6 (4) 721-731.

Holmes MGR and Young AR (2002c)
Estimating seasonal low flow statistics in ungauged catchments BHS 8th National Symposium - Birmingham, 2002

Holmes MGR, Young AR, Goodwin TH and Grew R (2005)
A catchment-based water resource decision-support tool for the United Kingdom
Environmental Modelling & Software Vol.20 Issue 2:197-202.

Young AR, Grew R & Holmes MGR (2003)
Low Flows 2000: a national water resources assessment and decision support tool.
Water Science & Technology Vol.48 No.10 pp 119-126