An enhanced version of the D-Risk decision support webtool for multi-scale management of water abstraction and drought risks in irrigated agriculture

Due to it having the lowest priority for water allocation during drought events and the consequent agronomic and economic impacts of abstraction restrictions, UK irrigated agriculture has been identified as a key business sector 'at risk'. An enhanced version of the D-Risk webtool has been developed to help agricultural stakeholders and catchment water managers to evaluate the joint multi-scale risks of abstraction restrictions (voluntary and mandatory) and having insufficient irrigation volumes during drought events. The webtool uses annual maximum potential soil moisture deficit as the agroclimate index to calculate monthly and annual volumetric irrigation demand for the selected crop mix, soil available water capacity and location. Simulated river flows are used to identify days not under abstraction restrictions. Annual probability distributions of irrigation deficit and licence utilisation (headroom) are derived from a monthly time-step water balance model that calculates whether the farm irrigation demand in each month can be met, taking account of river flow-based abstraction restrictions, daily and annual volumetric licensed abstraction limits, the licenced abstraction period(s) and any on-farm reservoir storage. The enhanced D-Risk tool provides a more holistic understanding of drought risk on irri-gated agriculture from individual farm to catchment scales and supports improved collaborative decision-making regarding future water sharing, water trading and on-farm reservoir investment to reduce business vulnerability to drought and regulatory change.