WEI + as an Indicator of Water Scarcity and Ecological Demand Issue

Different types of droughts, with a great number of indices which try to explain/categories them, exist in literature. Certain regions do not necessarily have the same drought pattern changes for different types of droughts. The socio-economic drought index WEI + of one country/region or catchment area is defined as a quotient of water abstraction and water sources availability (after deducting ecological demand), both with calculated returns. Water demand (or water use/abstraction) can be expressed as the total water demand (usually) or water demand for a certain purpose (water supply, irrigation, or industry). Both water demand and water availability can be examined at different time levels: mean annual, maximum (minimum) monthly, max (min) daily, etc. The reasons why these indices differ over time and across one region are different. Four larger and twenty smaller catchment areas in central Serbia were analyzed, the results of which are presented. River flows on hydrological stations (monthly basis data) have been used as water source availability. Available data for the 60-year period (1957–2016) has been included in the analyses. They have been split into two 30-year periods and differences between them have been considered. The adopted time levels are: 1) mean annual, and 2) 97%monthly flow which corresponds with maximum monthly demand. It has been shown that annual WEI + is still low, while 97%monthly is often higher than 0.5. An excessively high WEI + points to potential Environmental hazards, so Ecological demand must be considered. Due to climate change, and the increase in water demand, Ecological demand issues have become very debatable in dry areas worldwide. After presenting the methodology and results, the paper discusses all these issues.