Accounting for spatiotemporal complexities of drought in water accounting to inform integrated drought management

The different existing frameworks of Water Accounting (WA) techniques have proven to be useful tools for managing water in situations of water scarcity. The indices derived from WA procedures typically focus at informing decisions related to two different targets. A first group focuses on estimating water availability in different parts of a river basin. A second group focuses on the effects of human activities (interventions) on the water balance. Both are precious tools for decision making when the water is even scarcer, like in drought situations. However, their frameworks remain limited for an application to drought and drought impacts as it eludes many specificities proper to droughts. The aim of our study is to explore how WA techniques and indices can thus be adapted for integrated drought management. We based our approach on the water-balance data from the Banabuiú River Basin located in the semi-arid and drought-prone Northeast of Brazil. This area is the place of varied agricultural activities, rainfed or irrigated from a dense network of reservoirs. Droughts, from flash droughts to sometimes pluriannual, can affect the water balance of those reservoirs and the basin, and pose a challenge to meet all the agricultural needs. We direct our results towards the investigation of spatiotemporal scale issues. Indeed, water balance assessments often do not consider spatial variations in a river basin area and only report average annual situations. However, the duration of droughts or their impacts can extend beyond this reference period until sometimes becoming persistent to the system. The same applies for spatial-scale issues. Actions and processes happening at different physical scales and levels, inside and outside the basin, can modify the water balance. By addressing these spatiotemporal complexities, we aim to develop indices that will account for the human activities and enable to better inform decisions for integrated drought management.