Drought Risk Assessment Tool (DRAT) FAQs

SEPA measure rainfall and river flow data at hundreds of sites across Scotland. The data is accurate and representative of actual conditions in the environment, and it shows us when ecology is at risk. We also monitor groundwater and loch levels and use soil moisture data and rainfall forecasts from the Met Office. We compare the current conditions against long-term values to see how dry (or wet) it has been. This is what sets the levels of Early Warning, Alert and Moderate Scarcity. 

The highest level of water scarcity is Significant Scarcity. This is calculated in a different way. 

Significant Water Scarcity areas are smaller than the areas for water scarcity level as it’s important to be as representative as possible and avoid unnecessary restrictions to a wider, less impacted area. Broader areas shown in weekly maps reflect wider conditions but are not used for formal decisions about restrictions. 

Significant scarcity is reached when river flows have been very low for 30 or more days. We use a tool called the Drought Risk Assessment Tool (DRAT) to set significant scarcity level. 

DRAT is a network of flow gauging stations that SEPA monitor across Scotland and are used to set significant water scarcity when flows have been low for a sustained period of time. Data has been collected at these stations for a long period of time, so this allows us to give context to what is currently happening with the amount of flow in rivers relative to what you would normally expect. The river flow stations are each used as a representation of the conditions over an area, called a significant water scarcity area. The area and representative gauging stations are displayed on the tool.

Q95 is a recognised benchmark in hydrology. We use it as our low flow threshold. It’s calculated by looking at the 30-year dataset from 1991 to 2020 and using all the data in this period to look at the lowest five percent of flows in that time frame. Some years in the 30-year record flows will not get this low, and it’s unusual if this occurs for a prolonged period of time.  

SEPA begin warning about the risk of water scarcity as soon as the risk is identified. In 2025, this was in March following the publication of the Winter Recharge Report. We’ve been working with abstractors since areas reached “Alert” level, using advice, support and early conversations to help reduce pressure before mandatory restrictions are needed. The Q95 threshold is a regulatory point where the risk becomes too high to ignore, but action can and often does begin earlier. 

We have a dedicated team of staff who go out to flow stations regularly to measure and calibrate the flows. This is to make sure we have an accurate assessment of how much flow is currently in the river at any given time. The stations used are selected because they are representative of natural flows in the surrounding area, have accurate flow measurements, and a long period of record. 

Even if a part of the river appears to be flowing, it may not represent the full catchment conditions. The water you see might be needed to support wildlife and water quality further downstream. DRAT stations are chosen to be representative of conditions across the catchment, not just at one point, to ensure we protect the entire ecosystem.

We use a wide range of high-quality data to inform decisions, and we welcome information from water users. However, for consistency and to protect the wider environment, our regulatory decisions are based on nationally standardised, verified data from DRAT and other monitoring stations that reflect catchment-wide conditions.

Not immediately. Even if your local area sees rain, the entire catchment needs time to recover. The DRAT stations reflect that catchment-wide risk. Abstraction can only resume when the data confirms that conditions have improved across the whole area, and the ecological risk has reduced.

Scotland’s rivers and lochs are vital for wildlife, communities, farming, and industry. But they are also vulnerable. If we don’t protect our water environment now, it won’t be there into the future. Water is a shared resource, and everyone has a role in safeguarding it for the future.