Agriculture Reference
In-Depth Information
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the borehole, drilled by hand using simple machines. Such boreholes are equipped
with simple hand or foot pump
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a variety of modernized traditional water extraction devices using metal instead
of wood
Modern technologies
:
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excavation machines for large diameter wells
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motorized drilling rigs of various types for borehole drilling
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motorized pumps of various sizes and capacities
Modern technologies allow rapid execution and development of resources compared
to intermediate technology. In some cases, intermediate technologies are inefficient
and difficult for the extraction of large yields. Choice of technology should be
based on the above-mentioned criteria. As a guide, intermediate technologies are
to be used when local conditions, mainly depth of water table and type of geolog-
ical formations, allow for their use and when modest or moderate water yields are
sought. Modern technologies are to be used if rapid and/or large-scale development
is needed and if difficult hydrogeological conditions or lack of manpower do not
allow for simpler, less expensive methods.
Large-scale groundwater schemes involve great numbers of extraction sites. The
resource is invisible, its monitoring is complex. The operation of wells located on
private properties is in most cases beyond any control. The scattering of the sites
also creates specific problems. Most of the large-scale groundwater schemes fall
into the following categories taken separately or in combination:
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High-yield well fields equipped with powerful pumping stations for urban or
industrial supplies - less commonly for irrigation schemes
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Individual wells equipped with motorized pumps delivering moderate yields
(5-10 to 30-50 l/s) for irrigation or industrial needs including tourism.
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Open wells or tube wells for village or rangeland supply and small-scale irriga-
tion from which water is extracted using hand pump or wind energy. Nowadays,
solar pumps are used in some places.
5.3.3 Integrated Water Resources Management
5.3.3.1 Meaning of Integrated Water Resources Management
Many different uses of water resources are interdependent. For example, high irri-
gation demands and polluted drainage flows from agriculture mean less freshwater
for drinking or industrial use; contaminated municipal and industrial wastewater
pollutes rivers and threatens ecosystems; if water has to be left in a river to protect
fisheries and ecosystem, less can be diverted to grow crops. Integrated management
means that all the different uses of water resources are considered together. Water
allocations and management decisions consider the effects of each use on the others.
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