Rainwater harvesting (RWH) is an ancient technique to store water for domestic or agricultural use. It can be an important technology for regions where rainfall variability threatens water and food supplies and economic security. As such, it has the potential to be an important adaptation technology for resource-limited communities to counter the increased variability of rainfall patterns from climate change.
A review article in Environmental Science & Technology highlights the benefits and drawbacks of RWH in Tamil Nadu, India. Their work explores how rainwater harvesting might be beneficial in the context of modern socioeconomic and environmental pressures in the face of groundwater shortages and as a means of climate change adaptation.
Rainwater harvesting schemes in India are constructed using a series of earthen banks that take advantage of natural depressions in the terrain. During the monsoon season, the tanks fill up the hydrological network that can encompass more than a hundred tanks at different elevations that are linked via cascades. These tanks can provide extensive wetlands for avian species, flood control and enhance groundwater infiltration. Economically, they can raise local incomes by 50%.
Despite these benefits, RWH use has been in decline since India’s colonial era when the government constructed large dams, canals networks and irrigation wells. However, groundwater withdrawals have become unsustainable in recent years with withdrawals exceeding recharge in many parts of India. This, along with the threat of climate change, has led many to reconsider the potential of this ancient technology to be an important adaptation strategy in the face of increased precipitation variability.
The advantages of RWH include the fact that there are no transmission losses, which are common in canal systems, and RWH systems are replenished much faster than groundwater systems. Furthermore, the water stored in RWH systems can be shared among poor and rich farmers alike further spreading their socioeconomic benefit.
The authors continue to discuss the potential of these systems to be important adaptation tools for other regions including Sub-Saharan Africa. Regions such as these have abundant, albeit unexplored water resources. Since RWH is a low-cost, community-centered approach it can play an important role in improving crop security for small farmers facing an uncertain climate future.
Van Meter, K. J., Basu, N. B., Tate, E., & Wyckoff, J. (2014). Monsoon Harvests: The Living Legacies of Rainwater Harvesting Systems in South India. Environmental Science & Technology.
Deivalatha, A.; Ambujam, N. K. Sustainable agriculture productivity through restoration of tank irrigation system with stakeholder decision: Case study in rural tank ecosystem. Int. J. Biodivers. Conserv. 2011, 3, 527−539.