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Report
on Ground Water Resources Management (Upper Manyame Sub-Catchment
Area)
Environment
Africa
July 24, 2006
Background information
The promulgation of the
New Water Law in 1998 brought with it a paradaigm sheet from just
concentrating on surface Water Resources Management to a comprehensive
Water Resources Management, be it ground water or surface Water
as the two are all part of the hydrological cycle.
Most important to note is the aspect
of active stakeholder participation and the implementation of the
user-pays principle in today’s holistic approach to Water Resources
Management in Zimbabwe.
Ground water: Potential aquifer
capacity
The following are points
to be considered by UMSCC when allocating permits to groundwater
users.
- Groundwater is a finite and limited
resource which can be easily polluted and depleted. Over pumping
leads to aquifer dewatering. In cognizance of this, it means maximum
contact must be observed so as not to temper with ground water
that is being stored under natural conditions. Therefore it is
recommended to allocate only the recharge potential at any given
time and place.
- When allocating groundwater the geological
characteristics listed in item 2.1 below must be considered:-
General information on ground
water
Borehole water is water
lodged in what is called the "Zone of Permanent Saturation"
underground, at depths varying with the geological strata of the
locality. There is also an upper zone, of "Temporary Saturation",
which varies with the inflow and rainy season. Usually, this water
is very old, as much as 100 years, in fact in the Middle East, some
of the water is 4000 years old. Such water is generally free from
organic contaminants or pollutants, with certain reservations. Shallow
subterranean water deposits may be contaminated with surface water
runoff, especially sewage from human habitation. A pretty good rule
of thumb is not to use water less than 20 meters deep for human
consumption, so obviously shallow well water must be viewed with
great suspicion unless it is being used to water the garden/grass.
Most viable boreholes in Harare are of
the order of 50 meters deep and pretty well free of organic pollutants.
Please note that this is a general rule,
discounting natural fissures or man-made holes in the strata, through
which surface water may flow. Close proximity to septic tanks and
their soak ways are another source of organic pollutants, especially
in Harare. Care should be taken when siting boreholes, bearing this
important factor in mind. Please remember that abnormally, high
extraction rates of water from a borehole may result in such water
becoming contaminated, as evidenced in many parts of the world,
like Bangladesh.
At this junction, much has been written
about organic pollutants. These come chiefly from man or man’s activities
and may give rise to various ailments, especially the so called
"water borne bacteria" which will not be given in detail.
Other pollutants, really contaminants are the ones derived from
the geological strata, and these include soluble Lime, Magnesia
and many other mineral salts, usually of a minor nature. Such water
is called "brak" or "hard" and may cause problems
domestically with the furring or scaling of kettles, geysers and
steam irons.
Generally, borehole waters are moderate
to high hardness and frequently contain a relatively high amount
of dissolved Silica (Sand), which is harmless.
Again, undue abstraction rates will ecerberate
these problems. No mention has been made yet about the deleterious
elements that may unusually occur in borehole water and we are fortunately
and fairly free of such elements in our Harare borehole water. Hence,
it is these factors driving the UMSCC to be pro-active so as to
avoid excessive groundwater resource exploitation for the benefits
of our future generations and the environment in its entirety.
Forewarning
Finally, if any prospective
borehole owner wants to use this water for domestic purpose, I would
advise him to have a sample of the water tested by a reputable Laboratory,
both for organic and inorganic content, before using it domestically.
SubCatchment characteristics
Below are the aquifer
characteristics found in the Upper Manyame SubCatchment Council
which forms the basis of resource allocation to potential ground
water users within the SubCatchment area.
- Total Surface area of Geological Unit = 2
618 000 000m2
- Total estimated storage = 2
306 150 000m3/ann.
- Total recharge = 59
136 000m3/ann.
- Estimated usage = 56
803 125m3/ann.
- Total permitted usage to date = 13
959 296.5m3/ann.
- Estimated no. of groundwater users = 700
- Total no. of permits usage to date
= 163 (Prior to current borehole registration)
NB: The last two bullets have been
overtaken by events but the realistic scenario can only be published
after the ongoing groundwater registration exercise.
Water demand calculation
The following is the information that
can be used for one to estimate the annual demand though the demand
may not be met sometimes by the available resources.
- The average consumption per stand
for urban/domestic use is 900l/day excluding lawn irrigation/gardening.
This can be more than double if grass watering is intensive.
- Every property should be allocated
groundwater, that should be strictly recharged through that property
i.e. the area bounded by the property should be enough to generate
sufficient recharge which is thus estimated:-
* Recharge = 2%
of average annual rainfall in that area multiplied by total surface
area of the property.
Why Groundwater use needs to
be registered
Under the New Water Act, 1998, environment
is now considered a "Water User". Unlike
other water users, environment cannot come to the offices of UMSCC
or anywhere to lodge an application
for a water permit.
Hence, the registration of boreholes
and wells became imperative in the wake of the environmental and
pollution concerns as a direct threat by excessive utilization of
ground water being accelerated by erratic supplies of clear water
from the "City Fathers".
There are two paramount aspects to
be protected, thus:-
- Maintaining the water table at the
recommended level to avoid the inevitable environmental effects.
- Maintaining the base flows at the
recommended flow rates throughout the UMSCC river systems being
severely affected by pollution discharges from the industrialists.
If ground water is depleted, it pauses danger to the river life
as it will be subjected to unfriendly habitat conditions leading
to loss of animal as well as plant life.
Hence, it is this mammoth responsibility
that has left Upper Manyame SCC without an option but to take a
proactive position ahead of the loom environmental and pollution
disasters if this issue of groundwater utilization continues unchecked.
Services offered by the council
to its valuable clients/stakeholders
- Supervision of borehole drilling by
private Contractors to enhance quality service delivery.
- Advice on pump installations by reputable
service providers.
- Advice on borehole security features
- Advice on flow meter installations
- Advice on water quality testing (why
and where to have your borehole water tested).
Responsibilities of UMSCC
In brief, the functions of the SubCatchment
Council include the following others:
- Dispute resolution among water users.
- Catchment protection against pollution
and environmental degradation threatening both acceptable quantity
and quality of water.
- Regulating and supervision of the
exercise of water permits.
Expectations of UMSCC from stakeholders
- Willingness to declare all boreholes,
wells, Private dams and direct river abstractions.
- Exposing all unwilling stakeholders
utilizing the finite Resources without notifying the authorities.
- Co-ordinated approach to Water Resources
and pollution control and management.
Vision for the Year 2005/2006
Creating a realistic data
base in order to enhance a sustainable water resource allocation,
management and economic utilization to guarantee optimum socio-economic
benefits without undermining Environmental Justice and Integrity.
Enabling environment to achieve
the vision
- Registering of all water use, be it
ground or surface water within the whole SubCatchment area.
- Co-operation from all water users,
(as we have always thought that "together we will make a
difference").
Reminder
Remember Integrated Water Resources Management
is the key to realize sustainable Water Resource utilization in
a transparent manner in Zimbabwe in order to enhance:-
- Equitable distribution of the finite
resource to all users.
- Good water governance, Water allocation,
and, Management issues and utilization in a sustainable manner
without undermining the socio-economic value of water.
Visit the Environment
Africa fact
sheet
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