Rain is the primary source of almost all the freshwater sources, thus the pattern of rainfall matters a lot in the availability of these resources in any region. On the other hand, the climate change has not only resulted in speedy variance of rainfall intensity, but its locations and timings as well. This, we have recently observed in Pakistan in the year 2022, when heavy rains resulted in the extreme condition of flooding in major parts of the country, particularly in lower Punjab, Sindh and Balochistan. The most unusual pattern was observed in the lower parts of the country, which normally used to receive relatively very low rains in the past. The climate change can also be termed as a water crisis. Its impacts can be obvious through devastating floods, rise in sea levels, reduction in ice fields, and more wildfires and droughts in many parts of the world. Extreme weather conditions are making water scarcer, more unpredictable, and more polluted. Simultaneously, it is a matter of great concern that over 35 million acre feet of fresh water is allowed to discharge into the sea annually, whereas the consecutive devastating floods of 2010, 2014 and 2022 have constantly been sounding alarm bells for better management of this natural resource, which otherwise is resulting into the loss of multi-billion dollars yearly. 
Climatic/Metrological Mapping of Pakistan 
The climate of Pakistan can be divided into four main climatic regions or zones, i.e., highland climate, lowland climate, desert/arid climate and coastal/maritime climate. Highland climate zone includes all the mountainous regions of Pakistan, i.e., western and northern mountains. Lowland climatic zone includes all the plain areas of Pakistan, which include the whole Indus plain except the Indus delta. 
Desert/arid climate zone includes all the southeastern deserts like Cholistan, Nara and Tharparker whereas coastal climate zone includes the whole coastal strip from Makran coast to Karachi coast and Sindh coastal areas of Pakistan (climatic mapping of Pakistan). 
The metrological map of Pakistan reflects that the highland climate zone receives the highest rainfall in the country, whereas these mountainous areas act as the watershed of the lower parts the country as well. Hence, proper and better management of upper watershed areas has vital importance not only for the sustainability of local water resources, but for the long life of the existing main water reservoirs or those planned to be built in the future as well. 
Climate Change Adaption: Coping with Change
To address the negative impacts of climate change, various sustainable, affordable and scalable solutions can be adopted, like protecting natural buffers (e.g., mangroves forest), adopting climate-smart agriculture, reusing wastewater, harnessing groundwater and promoting rainwater harvesting in the country. Rainwater harvesting is more beneficial in areas which receive uneven rainfall throughout the year. It can be productive in multifold areas, including building resilience towards the negative impacts of climate change, addressing soil erosion issues and ensuring water supply during the dry spells. 
Rainwater harvesting (RWH) mainly consists of three methods; Rooftop RWH, Surface RWH (ponds, small dams), and groundwater recharging. It is a matter of great concern that we are far behind the desired level of utilizing/managing rainwater so far. Pakistan has been able to demonstrate these interventions as small-scale pilot programs only, some of which are mentioned below. 
Promotion of rainwater harvesting project by Earthquake Reconstruction and Rehabilitation Authority (ERRA) in the earthquake affected areas of Azad Jammu and Kashmir (AJK) and Khyber Pakhtunkhwa (KP) was implemented during 2010-14. This is the largest ever project of Rooftop RWH system not only in Pakistan, but even in the South Asia region too, wherein more than 40,000 building units were provided with RWH systems. This is not only the simplest way of providing water at the doorstep to the local population, but addresses the soil erosion issues of mountainous areas too, which is one of major causes of silting of two major reservoirs, i.e., Mangla and Tarbela Dams. 
Agency for Barani Areas Development (ABAD), Punjab has demonstrated substantive work of small and medium surface RWH systems in the northern parts of Punjab, whereas Pakistan Council of Research in Water Resources (PCRWR) did a pilot program in Thar area during the period 2006-08. 

Rainwater ponds and small dams have been developed by PCRWR in Thar area and ABAD in Upper Punjab respectively.
Capital Development Authority (CDA) did a pilot project of groundwater recharging with the assistance of United Nations Development Programme (UNDP) almost a decade ago. 
Potential Regions of Rainwater Harvesting in Pakistan 
In the context of implementing all three methods of RWH, the whole country can be divided into the following regions: 
▪ Northern/High Mountainous Parts. Rooftop RWH and small RWH ponds 
▪ Northern Sindh to North of Punjab, Northwest Balochistan and Northwest KP. Rooftop RWH, surface RWH and groundwater recharging.
▪ Lower South of Punjab, Northeast of Sindh to Coastal Areas (Sindh and Balochistan). Rooftop RWH and surface RWH.
▪ Northwest of Balochistan, Punjab and Sindh. Surface RWH, rooftop RWH and groundwater recharging. 
Conclusion and Recommendations
RWH systems have numerous benefits. They provide a supplemental water source, specifically during dry spells and allow individuals, municipal and local authorities to manage their water supplies, encouraging a conservation ethic by providing a visible indication of water usage. Rainwater harvesting also provides a safer alternate for drinking water in areas where groundwater or springs are highly polluted due to biological as well as chemical contaminants like Fluoride and Arsenic, etc. Last but not the least, rainwater harvesting helps us in managing the flash floods and conserve this precious ‘primary source’ of all freshwater resources for future productive use. 
The climate change impact warrants that all the above pilot initiatives (and any other, if overlooked), are now to be scaled up throughout the country, as and where feasible. Particularly, rooftop RWH, a simplest way of providing water in the northern parts of the country, such as Murree, Kotli Sattian, Galliyat, Swat, Mansehra, Muzaffarabad, Bagh, Rawalakot and similar areas can immediately be initiated with the active participation of local governments and beneficiary communities. 
Furthermore, for technical assistance and experience sharing, a close collaboration has to be made with regional and international organizations like South Asia Rainwater Network (SARNET), Lanka Rainwater Harvesting Forum (LRWHF), International Rainwater Harvesting Alliance (IRHA), America Rainwater Catchment System Association (ARCSA), and many more who are already working on similar interventions. 

The author is a Development Professional/Environmentalist and a member of Technical Committee of Pakistan Engineering Council on Green Building Codes. He is member of Steering Committee South Asia Rainwater Network (SARNET).
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