International Rainwater Catchment Systems Conference
Mannheim, Germany - September 2001
Rainwater Catchment in Humid and Arid Regions
Cost-effective Dimensioning of Artificial Rainwater Harvesting Storage
D. Walther and K. Thanasekaran
Centre for Environmental Studies
The existence of water harvesting systems in India have a long history
like gardabands in Baluchistan, kundis in the Thar desert of Rajasthan
or the temple tanks in Southern India. Although a wide range of experience
is available the development of the society makes it necessary to revise
these systems according the new requirements. Beyond any doubt the cost-effectiveness
plays nowadays an important role and has to be considered as one of the
factors for rainwater harvesting systems dimensioning.
The use of artificial storage facilities within a rainwater harvesting
system (RHS) requires exact calculations regarding their storage capacity
depending on its intensive costs. Annual amounts of rainfall have to be
statistically evaluated to estimate the probability of maximal rainfalls
as well as long dry periods. The size of the artificial storage is to
be chosen either by collecting the maximum of rainwater or to adjust it
according the requirements of the user.
This approach lacks a practical use in subtropical countries and includes
a high risk factor for the consumer's supply due to the complicated rain
patterns. The variation of amount of rainfall and rainfall intensities
in the range of several 100 % and unpredictable time range for droughts
complicates approaches for a consumer friendly cost-benefits. In comparison
to moderate climates artificial storage systems have to be considered
as buffer capacities for droughts.
An approach based on statistical tools like probability of rainfall,
return periods, storage equation shall make it possible to dimension a
rainwater harvesting system which are more cost-effective.
PDF of full document (6pp, 77kb)
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