It is a method for accumulating and saving rainwater from various elements such as rooftops, surface runoff, and other catchments.  Harvested water can be used for all domestic purposes like drinking water, cooking and washing etc. Moreover, this harvested water has a potential to meet agricultural and crop’s water needs according to the available economy, the storage can be managed either on-surface or sub-surface

Pakistan’s first urban rainwater harvesting system has been installed in the capital city Islamabad, the Daily Times reports. The collection tanks at the Faisal Mosque complex were funded by the city’s Capital Development Authority, and will provide clean drinking water while recharging the local water table for the city’s nearly 1 million residents.

Known as the Pilot Rainwater Harvesting Project, the initiative was developed in collaboration with the United Nations Development Program and the Pakistan Council of Research for Water Resources.

Pakistan is currently going through its worst water crisis due to being prone to natural disasters, demographical changes, and massive urbanization. This increase in migration toward urban areas is disrupting natural ecosystems which will ultimately increase the demand for household water in the country. According to the information by international agencies, water stress is increasing in Pakistan and for a country whose economy is highly dependent on agriculture, the situation appears alarming.

There are several sources of water for the country with 60% of the total rainwater coming from monsoon rains. Many glaciers feed the river system in Pakistan but the glacial melt off increases the risks of flooding. Moreover, the river Indus and its tributaries provide most of the water needed for irrigation in Pakistan.

Furthermore, the treated rainwater needs to be stored for its efficient use. In urban and rural areas, there exist vast opportunities to store rainwater by constructing rain-harvesting infrastructure by utilizing dry ponds, canals, and low-lying areas. Thus, during heavy rainfalls, such as those in monsoon, when rivers and canals overflow, extra water could be preserved in specially constructed dams, reservoirs, and underground tanks. This would not only prevent flooding of the urban areas in future, but also conserve the water for later use in times of crisis.

Rainwater Harvesting in Cholistan Desert

According to research collaborated by the Climate Change Adaptation Project of the World Wide Fund for Nature-Pakistan; “There is a dire need to utilize rainwater, particularly in the arid zones like Kohistan, Thar, Thal, and Cholistan for agriculture and livestock purposes. Groundwater in arid areas is mostly saline, and therefore, cannot be used”.

Cholistan is one of the main deserts covering an area of 2.6 million hectares where water scarcity is the fundamental problem for human and livestock population as most of the groundwater is highly saline. Rainfall is the only source of freshwater source, which occurs mostly during monsoon (July to September). Therefore, rainwater harvesting in the desert has crucial importance. The Pakistan Council of Research in Water Resources (PCRWR) Regional office Bahawalpur has been conducting research studies on rainwater harvesting since 1989 in the Cholistan desert by developing catchments through various techniques and constructing ponds with different storage capacities ranging between 3000 and 15000 m3. These ponds have been designed to collect maximum rainwater within the shortest possible time and to minimize seepage and evaporation losses. As a result of successful field research on rainwater harvesting system, PCRWR has developed 92 rainwater harvesting systems on pilot scale in Cholistan desert. Each system consists of storage reservoir, energy dissipater, silting basin, lined channel, and network of ditches in the watershed.

Rainwater should be harvested and stored by making earth medium size reservoirs. Rainwater from these ponds can be utilized efficiently for drinking and irrigating plants. These ponds have been designed to catch maximum rainwater within shortest possible time and avoiding maximum water losses. Each pond has been connected with the main catchment area through the main channel and network of ditches connecting all lowest points in the catchment area via small ponds to de-load rainwater from soil materials before reaching in the ponds. The rainwater stored in these ponds is utilized by the local Dingarh and surrounding area people (more than 1500 in number) for drinking. The water is taken by the women of the village and nomads clustered around the ponds during shortage of water.