Kidane, S.B. J. Agri. Environ. Sci. 8(1), 2023

Publication of College of Agriculture and Environmental Sciences, Bahir Dar University 1

Research Article

Groundwater-recharge estimation in Waja-Golesha Sub-basin, Northern Ethiopia:

An approach using WetSpass Model

Seyoum Bezabih Kidane

Department of Water resource Engineering and Management, Ethiopian Institute of Agricultural Research,

Ethiopia

Corresponding author: seyoumb18@gmail.com

Received: September 15, 2022; Received in revised form: January 23, 2023; Accepted: April 12, 2023

Abstract: Understanding the spatial variability of groundwater recharge in response to distributed Land-use, soil

texture, topography, groundwater level, and hydrometeorological parameters is significant when considering the

safety of groundwater resource development. Thus, this study aimed to estimate the groundwater recharge of the

Waja-Golesha watershed, in northern Ethiopia using the WetSpass (Water and Energy Transfer between, Soil,

Plants, and Atmosphere under quasi Steady State) hydrological model. The model inputs are prepared in the form of

20m grid size maps and attribute tables. The model parameters table was prepared using expert knowledge and

scientific literature. The modeling results of long-term spatial-temporal annual rainfall of 664.5 mm were

fractionated as 161.5 mm (24%) of runoff, 438.2 mm (71%) evapotranspiration, and the remaining 29 mm (5%) of

groundwater recharge. From the entire area of the sub-basin (532.6 km2), 1.6*105 cubic meters (m3) of water was

added to the groundwater through infiltration. The seasonal distribution of the recharge indicates that 72%

occurred in the wet season while the rest 28% resulted in the dry season. The evaluation of the modeled output

indicates that WetSpass works well to model the groundwater recharge of the Waja-Golesha sub-basin. To preserve

the resource's long-term viability, the balance between groundwater recharge and projected abstraction rates for

agriculture and domestic water supply must be considered in future groundwater resource development plans in the

watershed.

Keywords: Ethiopia, groundwater recharge, Waja-Golesha, WetSpass

This work is licensed under a Creative Commons Attribution 4.0 International License

1. Introduction

Groundwater is the largest source of fresh water and

one of the most curtail resources for human beings

(Mengistu et al., 2019). Due to its essential qualities

such as consistent temperature, wide distribution and

continuous availability, excellent natural quality,

limited vulnerability, low development cost, and

draught reliability, groundwater is a very critical and

dependable source of water supply in all climatic

regions. Sustainable utilization of groundwater

resources is crucial for the present and future

generations because groundwater is a finite and

vulnerable resource (Yenehun et al., 2017).

Consequently, Groundwater resource management

and sustainable use directly depend on knowledge of

groundwater recharge and potential (Fenta et al.,

2015). For efficient and sustainable groundwater

water resource management, evaluation of

groundwater recharge is a prerequisite and vital for

economic development (Arefayne and Abdi, 2015).

Kidane, S.B. J. Agri. Environ. Sci. 8(1), 2023

Publication of College of Agriculture and Environmental Sciences, Bahir Dar University 2

Depending on the source and mechanisms of

recharge, direct measurements, water balance

methods, tracer techniques, and empirical methods

are the techniques used to estimate groundwater

recharge (Simmers, 2017). As stated by Gidafie et al.,

(2016), space or time scale, range, and reliability of

recharge estimates are the factors considered during

selection of recharge estimation methods. WetSpass

(Water and Energy Transfer between Soil, Plants, and

Atmosphere under quasi Steady State) hydrological

model was used for this study by considering the

specially distributed factors such as land use, soil

texture, slope, and hydrometeorological parameters to

model long-term average spatial distribution of

groundwater recharge. This is because considering

groundwater resource safety is highly dependent on

understanding variability of recharge as a function of

variables such as land cover, soil type, slope,

groundwater depth, and hydrometeorological

parameters.

Rain-fed agriculture is the main activities in the case

of Ethiopian condition even if the rainfall variability

is high (Dereje and Nedaw, 2019). Less productivity

is the result of shortage and variability of rainfall

during the growing periods of crops. The mean

annual potential evapotranspiration which ranges

between 1900 and 2100 mm much greater than the

mean annual precipitation that ranges from 300 to

800 mm occurred in northern Ethiopia (Kahsay et al,

2018) and the area has a growing period of about 60

days and annual air temperature ranges from 16 to 27

°c. As a result, food security in the area is largely

dependent on supplementary irrigation.

Waja-Golesha watershed is one of the groundwater

based irrigation areas located in North Wollo zone of

Amhara national regional state. Local farmers fail to

keep soil moisture requirements for growing crops in

the area because of the erratic nature of rainfall (time

and space) distribution. Accordingly, groundwater

resource use in the area for agricultural development

is growing continuously. Therefore, groundwater

recharge estimation and groundwater potential

assessments were not supported adequately for

expanding irrigation in the area. Point estimate of

groundwater recharge for groundwater resource

development and potential site delineation was the

focus of previous studies (Ayenew et al., 2008;

Belay, 2015). However, groundwater recharge

estimation needs reliable methods (Rwanga, 2013).

Therefore, the objective of this study was to estimate

long-term seasonal/annual average spatial

groundwater recharge in the Waja-Golesha watershed

northern Ethiopia by adapting GIS-based WetSpass

model.

2. Materials and Methods

2.1. Description of the study area

Waja-Golesha watershed is located in northern part

of Ethiopia between latitude of 12°08′–12°19′N and

longitude of 39°23′–39°10′E (Figure 1). The study

area is bounded by the North-Western Ethiopian

Plateau in the west and the Afar Rift in the east with

an area of about 532.6 km

. It is among the

watersheds on the western edge of the Danakil basin.

The main physiographic features prevailing in the

area were north–south oriented mountains in the

west, a steep fault scarp in the east, a major graben

and isolated hills within the graben. The study area is

elongated intermountain graben filled with

quaternary sediments, bordered to the east and west

by rugged volcanic mountains with relatively high

elevation. The watershed is constituted of different

types of volcanic rocks and alluvial sediments. The

volcanic rocks (basalts, rhyolite, and granite) having

Tertiary age cover the majority of the area and are

found exposed in the surrounding mountains and

underlying the alluvium in the valley. The alluvium

sediments are mainly found occupying the valley

floor. Major and inferred faults, fractures, and

lineament having an alignment of N-S, NNW-SSE,

NW-SE, NNE-SSW, and NE-SW are the major

geological structures that are found in the catchment

(Tadesse et al., 2015).

The elevation of the watershed ranges from 1,352 m

within the valley floors to 3,032 m above sea level in

the western mountain ridges. The watershed is

characterized by an erratic, bimodal rainfall pattern

with the main rainy season lasting from late June to

early September. The highest rainfall record occurs in

July and August, whereas the short spring rainy

season extends from February to March. The average

monthly temperature of the Waja-Golesha watershed

varies from a minimum average of 4.7 °C in the Lasta

plateaus to a maximum average of 35.5 °C in the

Waja lowlands. The highest temperature is recorded