Water demand Requirements
Environmental flow requirement
- Environmental flow requirement recognizes the importance of releasing minimum water in rivers for ecological processes, downstream communities, and biodiversity.
- It refers to the allocation of water specifically for maintaining desired ecological states (instream flow requirement).
- Preserving natural flow characteristics (timing, frequency, duration, and magnitude) is crucial for freshwater ecosystem sustainability.
- Environmental flows began with a commitment to a "minimum flow" of around 10% of mean annual runoff.
- The aim is to sustain river ecosystems by securing a baseline water flow.
- Environmental flow requirements strike a balance between human water use and the preservation of ecological integrity.
The irrigation water requirement
- Irrigation water requirement is the difference between crop water requirements and effective precipitation.
- Calculation of irrigation water requirement requires crop, climate, and soil datasets of the study area.
- Red loamy soil type is assumed based on textural information and a preliminary assessment of surface water resources.
- Climatic data from the Batalagoda station, including reference evapotranspiration (ETo) and rainfall, are used for calculating the Irrigation Water Requirement (IWR).
- The primary objective of irrigation is to provide water when natural precipitation is insufficient to meet crop evapotranspiration needs.
Calculation of scheme Irrigation Water Requirement has been illustrated below;
Annual irrigation water requirement with system efficiency 0.5 (application efficiency 0.7 × conveyance efficacy 0.7) and 0.6 was found to be 24354 and 20295 cubic meter per hectare respectively. Monthly variation of the irrigation water is shown below Figure
