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By Katie Copley, Intern, communication and knowledge management (CKM) department, IWMI

A reservoir at Arali in Jaffna, Sri Lanka. Photo: Hamish John Appleby / IWMI
A reservoir at Arali in Jaffna, Sri Lanka. Photo: Hamish John Appleby / IWMI

William Rex, Senior Advisor at IWMI, shares his knowledge of integrated water storage and how it could provide a solution to the changing spatial and temporal distribution of water. In parallel a new report by IWMI together with the Global Water Partnership explains the challenges and the processes needed to improve integrated water storage worldwide and proposes a new way of thinking about water storage, as a service as opposed to a facility. The paper will be launched via a webinar, 24 February 2021 at 14:00 CET.

So, what’s meant by integrated water storage?

Simply, the challenge of water management is getting the right amount in the right place at the right time. Unfortunately, water is often distributed imperfectly for many people. For example, due to geography, farmers may not be able to access water for irrigation, or settlements may not have appropriate drinking water. Often, it’s about people needing water right now, even when there’s no rain. That’s when we turn to storage, to ensure there’s enough water during any season.

If you think historically, our ancestors originally settled by rivers or springs: they were relying on natural storage. People then began to build storage, such as dams and water tanks. Integrated storage is an attempt to think about both built and natural storage working together in unison.

How is water stored naturally?

The biggest form of natural water storage is in groundwater and aquifers, accounting for 97% of stored water. Yet, roughly 50% of groundwater is saline, so if people are going to use this untreated groundwater it would be like using water from the sea. Secondly, a lot of naturally stored water is in remote or inaccessible areas. So, while it may be technically feasible to extract the water it may not be economically feasible. Shallow groundwater is more accessible and easily refilled but at the same time can be easily depleted. Some areas of the world are rapidly depleting their groundwater, famously California, Saudi Arabia and the North West of India. Yet, in other areas, most notably Africa, they are underexploiting groundwater.

Mountain glaciers also contain a lot of storage, as do lakes: soil, wetlands. Forests also store small amounts of water.

Why is integrated water storage important?

Integrated water storage is important for basic socio-economic development purposes, as countries need storage in order to develop cities and grow crops. Another key issue is around climate change: as we experience increased water variability the challenge is that many countries are already starting with a water storage deficit.

Can you tell us a little bit more about this challenge of the storage gap?

The hypothesis in our new paper is that we believe there’s a growing water storage gap between supply and demand. On the demand side of the equation, we see an increased need for water as demographics and economies change. Developed nations like Japan, USA and European countries have passed their peak water demand and as their economies have become more efficient, they have less need for these water sources.

On the supply side of the equation, we are seeing the degradation of nature and significant reductions in groundwater, lakes and glaciers all of which are a function of climate change and human activity. Although soil moisture change is relatively minor, forests are declining and wetlands have shrunk by roughly 40%. There has been a massive amount of dam construction over the past 50 years: human behavior is still damaging the environment and climate, changing the natural water cycle and reducing the amount of storage.

We need to talk about integrated storage and hydraulics systems in terms of a service rather than a facility. The concern is not about the volume of water stored; it is about the reliability of the water supply. Supply for a farmer may be less important than a reliable supply to a nuclear power station. Our argument is basically trying to translate water storage into a service, providing a certain rate of reliability and quality. From there we then consider the best combination of storage to meet that service hence the notion of integrated water storage.

So, what can IWMI do?

The IWMI challenge is to develop tools that will help answer the equation of supply and demand. Different combinations of storage for different cities. We need to be positioning ourselves at the cutting edge of thinking around storage and a big part of that is trying to shift the agenda and the way the world thinks about storage and to face up to the scale of the data gaps that exist.

What are your thoughts?

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