Estimating the spatial distribution of evapotranspiration within the Pra River Basin of Ghana

Abstract

It is important in water resource planning to accurately estimate the spatial distribution of evapotranspiration (ET) as an input parameter for hydrological studies. Although, conventional pan evaporation, lysimetric and eddy covariance techniques have been used, they only estimate point values. Hence, this study aimed at estimating the spatial distribution of ET within the Pra River Basin (a forest ecological zone) of Ghana, using cloud-free Landsat 8 (OLI/TIRS) satellite images employing the SEBAL methodology. The study further estimates the spatial distribution ET in relation to major climatic variables, Land Use Land Cover (LULC) types and energy balance components. The overall spatial distribution of ET had a mean value of 5.63 mm/day. Spatial distribution of ET (mm/ day) for water body (5.51-7.81) and uncultivated forest (5.10-7.71) were high, while moderately average values were observed for logged forest (4.80-7.51). Settlement and bare landscapes observed low rates ((2.05-5.10) mm/day). Spatially, ET was higher in the upper western, central and the eastern parts of the basin, but lower in the northern part and pockets of areas at the southern part of the basin where settlement/bare landscape and logged forest dominate. Areas with high temperature and high solar radiation experiences high ET, while low wind speed, low to average temperature and solar radiation areas experience low ET. Also, areas with both high net radiation and ground heat flux but low to average sensible heat flux experiences high ET and vice versa. Linear regression analysis showed good fit with slope of 0.76 and R 2 of 0.93 indicating that 93 % of the variations in observed field measurement of ET fitted perfectly well with ET distributions generated by the SEBAL model.

Spatio-Temporal Variations of Reference Evapotranspiration in Western Iran

“…In 2017, the same pattern occurred in the distribution of ET0 by this difference that data is reduced. Nsiah et al (2021) showed a variation of ET was higher in the western, central, and eastern parts of the Pra River Basin of Ghana, but it was lower in the northern and southern parts of the basin where there are many settlements and forests. Chang et al (2023) showed that in Tibetan Plateau's from the southeast to the northwest the multiyear mean annual ET decreased.…”

“…The results showed a decrease in the climate balance due to a decrease in precipitation and an increase in ET0 during the study period. Nsiah et al (2021) assessed the spatial changes of evapotranspiration in the Pra River Basin of Ghana. The spatial variation of ET was higher in the western, central, and eastern parts of the basin, but it was lower in the northern part and parts of the southern part of the basin where there are many settlements and forests.…”

A Review on Evapotranspiration Estimation in Agricultural Water Management: Past, Present, and Future

“…Remote sensing can also be used for crop classification, crop monitoring during the growth season, and crop production assessment. In this regard, the remote sensing technology with global positioning systems (GPS) and geographical information systems (GIS) can be used to improve the efficiency in agricultural activities such as farmland extent estimation, crop growth stages monitoring, soil moisture and fertility evaluation, crop stress detection, diseases and pest disperse, drought and flood situations monitoring, and weather forecasting [7,64,[79][80][81].…”

GIS-Based Water Budget Estimation in the Pra Basin using Remote Sensing Data

“…The water budget allows for the water circulation rate and changes in water retention in all sections of the atmosphere, land surface, and sub-surface (Chandra et al, 2022). Through evaporation, water from the Earth enters the atmosphere and is lost to it as precipitation, primarily rain or snow (Nsiah et al, 2021). Water that seeps through the ground can stay in the unsaturated zone, where it will probably evaporate or transpire from plants and return to the atmosphere.…”