Strengths

  • Provides an important water resource for agricultural and domestic uses.
  • Recharges groundwater.
  • Recharges bore wells/dug wells.
  • Maintains soil moisture of catchment area.
  • Provides an independent water supply for regions with water restrictions or when there is drought.
  • Manages flooding, particularly in downstream catchment area.

Limitation

  • Rainwater harvesting systems require regular maintenance. They can become breeding grounds for rodents, mosquitoes, algae growth, insects and lizards if they are not properly maintained.
  • If used for agricultural or domestic purposes, a possibility of high rates of water loss due to infiltration into the ground can be a problem.
  • Not having good rainfall makes the system less cost-effective.

Rainwater harvesting (Land)

Application: Aquifers, bore well/ dug well, buildings, farms, houses, markets, reservoirs

Description: Rainwater harvesting with a land surface catchment is a technique that provides more opportunity for collecting rainwater and stormwater from a larger surface catchment area in comparison to a rooftop catchment technique. The land surface catchment technique varies from small scale to large scale reservoir rain harvesting systems depending on the geographic area and engineering design techniques. It can be designed with low cost earthen dams, dykes and canals to collect and storage the water. The dams are constructed at the lower part of the catchment or reservoir areas to retain the flows of small creeks and streams and surface water runoff in the storage reservoir system. The sluice gate of the canal is an important component of the system. It helps to retain the water, and discharge it if overflowing in order to manage flooding downstream and upstream in the catchment. The harvested water can be used as a water resource for agricultural purposes, livestock, and domestic use with proper treatment. It can also be used as drinking water, longer-term storage and to recharge bore wells or dug wells and groundwater.

Contribution to climate resilience: Rainwater harvesting ponds improve drought resilience by increasing the availability of water for agriculture, livestock, and household uses such as washing and laundry. They store water during heavy rainfall in the wet season and reduce scarcity during the dry season - both events likely to become more severe with climate change. Rainwater harvesting ponds are particularly suited to households which cannot install rainwater tanks due to sloping land or geographical isolation.

Supplementary sources of information:

http://www.fao.org/docrep/R7488E/r7488e00.htm#Contents

http://www.unwater.org/downloads/Rainwater_Harvesting_090310b.pdf

http://www.unep.or.jp/ietc/Publications/Urban/UrbanEnv-2/3.asp

http://www.gdrc.org/uem/water/rainwater/introduction.html

Background image credit: https://commons.wikimedia.org/wiki/File:Rainwater_Harvesting_and_Plastic_Pond_2.JPG

This resilience-building measure is sourced from the Water Resource Adaptation Guide (2019) published by the National Council for Sustainable Development at the Ministry of Environment in Cambodia. The full Guide is available to download at URL https://ncsd.moe.gov.kh/sites/default/files/2019-10/Water%20Resources%20Adaptation%20Guide_March%202019_En.pdf