The impact of urban groundwater upon surface water - eTheses ...

MONITORING NETWORKS AND METHODS
Environment Agency data from gauging stations at Bescot, Calthorpe and Water Orton were
inspected and recession periods selected for analyses during periods of dry weather flow to
avoid the impact of run-off. Exponential decay curves and semilog straight lines for the two
different methods were fitted through the minimum values for each day to reduce the impact
of intermittent sources such as the sewage treatment works (Appendix 17). The basin
constants derived for each recession were compared and average values taken. These
constants allow calculation of baseflow after any time period and are useful in calculating the
maximum and minimum values to be expected for drought or high baseflow scenarios. The
basin constants may be compared between catchment areas and between different time
periods (years) to assess variability in the hydrogeological regime.
The baseflow component for the 24 km section of river between the gauging stations may be
derived by subtracting the upstream baseflow (Bescot G.S.) and the major tributary baseflow
(Rea at Calthorpe G.S.) from the baseflow at the downstream end (Water Orton). Further
subtractions must be made for known industrial discharges and smaller tributaries. Data for
these additional discharges are difficult to find as industry seldom discharges continuously at
its consent levels and tributary flow is variable. Other unknown inputs will most certainly be
incorporated within the baseflow estimates in addition to the groundwater contribution.
The 23.8 km of river channel between the gauging stations incorporates groundwater inputs
from the following underlying geological units:
Mercia mudstone (7.8 km);
Triassic sandstone (7.4 km):
Carboniferous coal measures (8.5 km).
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