Key Messages

Rethinking water storage

Climate change necessitates a fundamental rethink of the way water resources, and particularly water storage options, are planned and managed. In all situations, maximizing the benefits and minimizing the costs of water storage options will, as in the past (but not commonly done), require consideration of a wide range of complex and interrelated hydrological, social, economic and environmental factors. However, in a departure from the past, planning needs to be much more integrated across a range of levels and scales with much greater consideration of the full range of possible options. To date, although there have been many studies on the effects of climate change on hydrological regimes, there has been very little systematic research into the potential impacts of climate change on different water storage options or how to plan and manage water storage under a changed climate. Despite the high levels of uncertainty it is important that climate change projections and scenarios are used to improve planning of all storage types.

Key to planning and management of water storage is determining current and future needs and making appropriate choices from the suite of storage options available. In any given situation, this requires understanding of a range of biophysical and socioeconomic issues that influence the need, effectiveness and suitability of the different water-storage options, both in isolation and within systems comprising several types. In the past, there has generally been little explicit consideration of these issues, even for large dam construction. For other options, where planning is generally less formalized, needs are usually regarded as self-evident and alternative options are only rarely considered. The impacts of different options on existing and future storage are seldom well thought-out. The details of climate change are unknown, so planning must allow for greater uncertainty. Future water storage must be more reliable and resilient and less vulnerable than in the past. All water storage options have strong comparative advantages under specific spatiotemporal conditions.. Hence, storage ‘systems’ that combine and build on complementarities of different storage types are likely to be more effective.

The Water Storage Continuum:

Source: Adapted from McCartney, M.; Smakhtin, V. 2010. Water storage in an era of climate change: Addressing the challenge of increasing rainfall variability. Blue Paper. Colombo, Sri Lanka: International Water Management Institute.