10th International Rainwater Catchment Systems Conference
"Rainwater International 2001"
Mannheim, Germany - September 2001

Section 2: Rainwater Catchment in Humid and Arid Regions

Paper 2.16

Cost-effective Dimensioning of Artificial Rainwater Harvesting Storage Systems

D. Walther and K. Thanasekaran
GTZ Chennai
Centre for Environmental Studies
Anna University
Chennai-25
India
email: gtz_ces@vsnl.com

Abstract

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 available to members (6pp, 77kb)