Geoscience Reference
In-Depth Information
amount of abstracted water for Birmingham comes
from the Elan valley in Wales, a natural tributary of
the river Wye which drains into the Bristol Channel
on the west coast of England. So in addition to
causing diurnal fluctuations in the river Tame
downstream of Birmingham, the waste water
effluent is part of a water transfer across Great
Britain. In a study into low flows in the United
Kingdom (i.e. England, Wales, Scotland and
Northern Ireland), Gustard
et al
. (1992) identified
that 37 per cent of flow gauges were measuring flow
regimes subject to artificial influence such as
abstraction, effluent discharge or reservoir
regulation of the river. This degree of flow alteration
is a reflection of the high degree of urbanisation and
the high percentage of the population living in an
urban environment in the United Kingdom.
Urban snow melt
The influence of urbanisation on snow melt is com-
plicated. Semandi-Davies (1998) suggests that melt
intensities are generally increased in an urban area,
although shading may reduce melt in some areas.
Overall there is a greater volume of water in the
early thaw from an urban area when compared to a
rural area (Taylor and Roth, 1979; Semandi-Davies,
1998). This may be complicated by snow clearance
operations, particularly if the cleared snow is placed
in storage areas for later melting (Jones, 1997). In
this case the greater mass of snow in a small area will
cause a slower melt than if it were distributed
throughout the streets.
Waste water input and water extraction
Human intervention in the hydrological regime
of a river may be in the form of extraction (for
irrigation or potable supply) or additional water
from waste water treatment plants. The amount of
water discharged from a sewage treatment works
into a river may cause a significant alteration to the
flow regime. At periods of low flow 44 per cent of
the river Trent (a major river draining eastern
England) may comprise water derived from waste
water effluent (Farrimond, 1980 quoted in Newson,
1995). There are times when the river Lea (a
tributary of the Thames, flowing through north-east
London) is composed of completely recycled water,
which may have been through more than one sew-
age works. Jones has a startling diagram (1997:
227, Figure 7.9) showing very large diurnal varia-
tions in the river Tame that can be attributed to
sewage effluent flows from the city of Birmingham,
England. In this case the lowest flow occurs at 6 a.m.
with a rapid rise in effluent flow that by mid-
morning has boosted flow in the river Tame by
around 40 per cent (
SUMMARY
The case studies and different sections in this
chapter have shown that there are many aspects of
change in hydrology to be considered. Equally there
are different management structures and principles
that can be used to manage the change. In order to
understand and make predictions concerning
change it is essential to understand the
fundamentals of hydrology: how processes operate
in time and space; how to measure and estimate the
rates of flux for those processes; and how to analyse
the resultant data. The fundamental processes do not
change; it is their rates of flux in different locations
that alter. It is fundamentally important that
hydrology as a science is investigating these rates of
change, and finding new ways of looking at the
scales of change in the next 100 years.
≈
2.3 cumecs) (Jones, 1997).
The extra flow that a river derives from sewage
effluent may be especially significant if the waste
water effluent has been abstracted from another
catchment. The water in the river Tame naturally
flows into the river Trent before flowing into the
North Sea on the east coast of England. A large
ESSAY QUESTIONS
1
Discuss how well the principles of
Integrated Water Resource
Management are applied to the
management of a catchment near you.
