## 1 Introduction  
Water is a vital and finite natural resource. The water demand for different sectors, such as agriculture, domestic, industry, and energy, is continuously rising to meet the needs of the growing population [1]. Within the last 100 years, global water demand has escalated by 600% [2]. The shrinking supply and expanding demand of fresh water, due to rapid growth in population, changing consumption patterns, and socio-economic development around the world, poses formidable threats to the global fresh water systems [3]. Hence, managing water resources is essential for sustaining lives on earth, socio-economic development, a healthy environment, and the well-being of humans [4, 5]. Water accounting opts for the water balance approach; hence, various domains of inflows and outflows must be specified, according to the mass conservation approach [6]. It also helps recognize the intrinsic causes of problems pertinent to the water and provides viable data and information for resolving obstacles in a particular area over time [7]. River basins are natural, unique, hydrologically self-contained, and fundamental entities of water resource planning and management [8, 9, 10]. They can be used to estimate the water budget (water supply, demand, and storage) of regional water systems. Among the different water budgeting approaches, as described by [PERSON] and [PERSON] [11] and [PERSON] [12], nowadays, a new framework, namely water accounting plus (WA+), is being widely used [13] for water accounting in river basins. The International Water Management Institute (IWMI)-based WA tool, developed by [PERSON] and [PERSON] [6], and the recently designed WA+ framework replaced Molden [14]. IHE-Delft has developed the WA+ framework in partnership with the World Water Assessment Program (WWAP), IWMI and FAO. It works based on the method introduced by the IWMI [14]. WA+ is a novel water accounting framework that relies on remote sensing data and combines the depletion method (e.g., IWMI Water Accounting) of water accounting with the flow method (e.g., UN SEEA-WATER) of water accounting [13]. The WA+ works on the water balance principle [15] and has been specifically designed and built to exploit remote sensing measurements of hydrological variables and land use in a spatio-temporally distributed manner. WA+ summarizes the status of water resources in a basin using easily understandable spatial maps, tables, and sheets. WA+ describes the water resource of river basins based on eight fact sheets [13]. [PERSON] and [PERSON] [16], [PERSON] et al. [17], [PERSON] et al. [12], [PERSON] et al. [18], [PERSON] et al. [19], and [PERSON] et al. [13] used earth observation data to estimate the water accounts of river basins in Sri Lanka, Okavango basin, Nile basin, East Rapti basin, Awash basin, and Indus basin, respectively. The IHE Delft Institute with FAO has employed WA+ over the Nile River basin for a water accounting study using remotely sensed datasets [20], and evapotranspiration (ETa) at the basin level was often recorded higher than the precipitation from 2009 to 2019. The study also unveils that, from the water resource perspective, the potential for agricultural expansion is limited in the Nile basin. The FAO and IHE Delft [20] have also used WA+ in the Niger River basin and found a balanced water budget throughout 2009-2015, despite the variability in the amount and distribution of the evapotranspiration and precipitation at the basin level. FAO and IHE Delft [20] have used WA+ in the basin of Awash River, Ethiopia. Analysis revealed that the spatial pattern of actual evapotranspiration was almost consistent for the whole basin, except at the highlands, where actual evapotranspiration exceeds precipitation in the basin. FAO and IHE Delft [20] have employed WA+ for a water accounting study in the Jordan River basin, Jordan. It was found that the Water Productivity (WaPOR) database of FAO was not uniformly applicable and showed a noticeable discrepancy in the estimation of the water balance for the Jordan River basin.