Page 164 - CIWA Water Data Revolution Overview Report

fraction, it quantifies the water used for irrigated agricultural ET relative to the total water
used in agricultural ET.

Irrigated Evapotranspiration Fraction =

Basin closure (%)
The basin closure is calculated as total amount of water available that is utilized within a basin.

=

Any basin with estimates closer to 100% indicate basin closure – indicating most to all water
availability in the basin is currently consumed with in the basin. A smaller value indicates that
water is available in the basin.

3.3 Water Balance

The Water balance, also known as the hydrologic balance or water budget, is a fundamental
concept in hydrology. It refers to the equilibrium or accounting of water inputs, outputs,
and storage within a defined area, such as a watershed, catchment, or region. The water
balance equation helps quantify the movement and distribution of water in various forms
through the Earth's hydrological cycle.
Within the water accounting framework, water balance of a river basin is quantified and
presented using a number of hydrologic variables. Unlike most hydrologic studies where the
water balance is mostly represented by the key hydrologic variables such as Precipitation,
evapotranspiration, discharge and change in storage, the water accounting framework
derives a variety of hydrologic parameters. A full list of water balance indicators quantified
in the water accounting framework are presented in Table 1.
The figure below shows basin input parameters on the left side and basin output parameters
on the right side. The WA+ framework tracks both the flow and consumption (depletion) that
occur within the basin as water moves from the inlet to the outlet of the basin. The depletion
accounting is used to estimate how much of water us consumed over different landscapes.
This is summarized under four broad categories of land cover/land use – Protected-
conservation areas with minimal changes in land and/or water management, Utilized- are
areas with limited human influence and can include forest, natural pastures, savannahs and
deserts, Modified- areas that are significantly modified by human activities usually for rainfed
agriculture and Managed water use- are land use classes that are significantly modified for
agriculture and include water purposefully withdrawn from the surface or groundwater
sources for use The flow accounting derives a bunch of parameters such as exploitable water,