Drought Management: Leveraging Data and Models for Effective Adaptation

• Drought modeling requires detailed data on precipitation, soil moisture, plant types, and water usage.

• Drought adaptation measures include transporting water, improving water use efficiency, and growing drought-tolerant crops.

• Insurance and retrofitting buildings to reduce water demand are key strategies for managing the financial impacts of drought.

For credible modelling of the physical risks from drought, data are needed.

Drought is about less water coming into a location than is needed for all uses, such as for crops, livestock, navigation, drinking, and hygiene. Water coming in can be from precipitation, surface water flows, and groundwater flows. Aside from uses, water going out is mainly from evapotranspiration, surface water flows, and ground water flows.

Precipitation data are just about measuring the weather: How much water falls, at what rate, and in what locations?

Precipitation type is important as well. Rain soaks into the soil, supporting crops, while running off and reducing the amount of water locally. Snow could lie for a while, accumulating and then providing irrigation when it melts in the spring. Hail might bring a lot of solid water, but can damage assets as much as drought.

Measuring precipitation over a wide area at high resolution complements data on flow measurements for rivers and aquifers. A location might have few surface waterways, but plenty of underground streams, indicating that drought is less likely. Or groundwater might be limited, but plenty of wetlands, lakes, and rivers are available for water.

Data on soil moisture and plant types contribute to determining the general drought conditions of an area. Plant species types and numbers lead to calculations regarding their water needs. A prevalence of water-guzzling trees suggests a fairly wet climate – or a lot of imports – but also major difficulties if precipitation dips below average. Dry-tolerant species suggest low water needs due to low water availability.

Nature’s water use is part of the equation for water going out. A major variable in water loss from an area is evapotranspiration which, as the name suggests, combines evaporation (surface water changing to water vapour or water gas) and transpiration (water loss from plants to the atmosphere).

Evapotranspiration rates can be measured directly, although it is not easy to do so over large areas, so estimation techniques are preferred, using weather data including air temperature, humidity, sunshine hours, and wind speed, in addition to plant cover over the area in question.

Another major contribution to water going out, and so a contribution to drought, is human water consumption. These data are usually available, although can only be an estimate because unregulated and unmonitored water consumption can be significant. As well, some water use does not impact water availability, because the wastewater is discharged locally (cleaned or uncleaned) and can be re-used.

Water consumption changes over time, for people and nature. The number of people and their average rate and amount of water use varies. A wildfire can create a step change in an ecosystem’s water uptake and evapotranspiration, followed by a slower trend as vegetation re-grows.

Weather and climate have many variabilities, including large-scale multi-decade changes. Consequently, long-term datasets are essential for accurate and precise models to assist with drought forecasts and projections.

Even five years of highly detailed data would not suffice to understand variations in water availability due to the El Niño - Southern Oscillation (ENSO) which runs on a timeframe of 2-5 years.

Using available data and model outputs, drought adaptation measures can be selected and implemented to reduce the costs of drought to assets.

Often, the go-to adaptation measure is transporting water to where it is needed.

Pipes, aqueducts, channels, canals, and trucks are all used to provide water in arid areas. Aridland cities such as Los Angeles and Tehran have been built by channelling water from elsewhere.

This option is expensive to build and maintain. It leads to huge problems if the system breaks, which it can in the earthquakes plaguing both Los Angeles and Tehran. It can also create a permanent drought in the places where the water is extracted from. One advantage is that channels and canals can be used for transport.

Insurance is key for adaptation by agriculture and water supply systems. A competent and responsive company makes a solid profit from their insurance products and services while paying out fully and promptly to clients in need.

Whether or not insurance is a long-term adaptation solution remains an open question.

The more frequent the payouts, the more likely that premiums will rise and insurance could become unaffordable for some. If models or data lead to inadequate risk analyses, then no matter how creative their products and services, insurance companies could go bankrupt, leaving their clients in the lurch.

Reducing water demand should be a priority retrofit and adaptation measure for buildings. One of the worst offenders is leaks, especially in old pipes. US water utilities lose a staggering 17% of their delivered water to leaks.

From industrial washers to home showers, low-flow high-pressure options easily pay back the investment in them through much-reduced water costs.

Reusing water saves even more. Some uses require clean water, but if it is then not too dirty, it can be piped and used elsewhere. At home, water flowing into sinks, showers, baths, dishwashers, and washing machines should be clean. Their output water could be redirected into flush toilets or gardens.

Diversification into drought-tolerant crops can widen the range of arable land and land that remains arable as water availability fluctuates. The best choices would be plants that are naturally water conservationists or drought resistant. But they should not lose their ability to deal with other difficulties such as floods, weeds, and pests in order to increase their survivability and yields in droughts. Nor should they harm local ecosystems.

Many offers of drought-tolerant plants are based on genetically modified organisms which have their risks as well as their benefits. Replacements and increases in drought tolerance must never cause more problems than they solve.

Ultimately, to address the physical risks from drought in the most cost-effective manner, Climate X solutions can tell asset managers how much cheaper prevention is than cure. They can also offer a suite of adaptation measures from which to choose.