WRA expertise - Artificial influences of flow

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Artificial Influences
The increasing need to optimise water resources brings with it an increasing need to understand and to quantify all components of flow in a river or aquifer system. For analysis of water resources, with the aim of optimising existing resources or introducing new ones, there is a need for a "natural" flow record. That is a flow record which would have occurred had there been no anthropogenic effects. Whilst flows in most rivers of significance for water resources have been measured for many years, and often, for important rivers, for several decades, the same is not true of the factors such as abstractions and discharges, which change the flow regime. Often where these factors have been measured there are gaps in the records and in many cases relatively important factors have not even been measured.
							Some of the principal forms of artificial influence are: public water supply and sewage treatment works, impounding reservoirs, spray irrigation, small consumptive abstractions, canals, groundwater pumping, inter-basin transfer, catchwaters, power stations, mine/quarry de-watering. All of these have their own characteristics which affects the way they are dealt with. For example whilst public water supply abstractions and sewage discharge are linked, the linkage, being a result not only of supply but of losses and complex distribution systems, in not always easy to determine.
Many of the forms of artificial influence reflect underlying trends in water use which, whilst they do not necessarily explain all the variability, can go some way to achieving a consistent explanation for it. Some of the factors are: Population growth (e.g. public water supply), Season (e.g. irrigation), Economics (e.g. steel production), Periodicity (e.g. diurnal variation).

Experience as a company River Rother (Sussex) Flow data were collected for the Rother at Udiam and two upstream flow gauging stations. Data were also collected on precipitation and PET and artificial influences. HYSIM was used to infill gaps in the flow record taking account of these influences. Sussex Ouse The WRA catchment model, HYSIM, was used with all available rainfall, discharge, PE and artificial influence data. The effects of various patterns of abstraction and discharge could be simulated as could the consequences of climatic change (by modifying rainfall or PE sequences) Resources study of Severn and Trent WRA worked in two main areas. Firstly it was necessary to produce a long-term flow record for all the major surface resources Secondly, using this data the RESSIM model was updated and modified to simulate all the surface resources of Severn-Trent. The flows have been calculated in such a way that the effects of different patterns of artificial influences (irrigation, leakage control and sewage) can be studied. The resource model has enabled a complete re-evaluation of the reliability of the surface resources of Severn-Trent to be carried out. During this project we also became increasingly aware of linking the naturalisation process to the resource simulation process; unless they are calculated on the same basis than inconsistency can be introduced into the calculation. SNIFFER (Scotland and Northern Ireland Forum for Environment Research) We are currently working on a project with SNIFFER. The clients identified the need to develop a consistent methodology which could be used by the various organisations with water resource responsibilities in the two countries. Existing programs from WRA, HYSIM and RESSIM are being adapted to meet the particular needs. Reservoir study for British Waterways WRA produced a daily inflow sequence for all 16 reservoirs forming part of the study. As use of water for canals is often a significant artificial influence this gave us valuable insight to this particular problem.					In addition the Principals have also worked in: Water resource modelling for Thames Water Operating through the sister company, Oxford Scientific Software, WRA staff have provided Water Resource Modelling expertise to Thames Water over many years. This has involved the understanding of the many artificial influences in the Thames catchment. In particular the recent re-write of the London model simulates the behaviour of the Thames and Lee within London and models the artificial influences that take place in that area.