The Role of Small Reservoirs in a Water Scarcity Scenario: a Computational Approach

This paper presents the evaluation and management of water resources at the basin scale, focusing on small reservoirs. Due to a lack of knowledge on these untapped resources, a semiautomatic procedure for their surface area estimation is presented. Multispectral images from the Pleiades satellite were used to extract water bodies from a combination of different bands. In particular, the normalized difference water index (NDWI) was used to evaluate the presence or absence of water. This methodology was applied in a test area located in the upper Tiber River Basin. The performance for identifying and analysing small reservoirs was determined by comparing the satellite information with a reference database. The potential volume available from the investigated small reservoirs was compared with the water deficit derived from a decision support simulation model at the basin/subbasin scale, which studies water allocation for multipurpose uses. Five irrigation districts were analysed. For three of these districts, more than 60% of the annual deficit can be balanced with the volume stored in small reservoirs. To date, water scarcity conditions have been increasingly frequent, so resilience in water resource management is a key requirement. Therefore, it is essential to evaluate the recovery and reuse of small reservoirs to strongly support water use, particularly irrigation and environmental uses.