Predicting Reference Evaporation for the Ethiopian Highlands

Adem, Anwar A.; Aynalem, Dessalew W.; Tilahun, Seifu A.; Steenhuis, Tammo S.

doi:10.4236/jwarp.2017.911081

Cited by 16 publications

(10 citation statements)

References 26 publications

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“…Evaporation from the open water body, which is one of the major water balance terms, was calculated by the Penman-Monteith method for the Bahir Dar station by Adem et al [52] from the monthly temperature sunshine hours, humidity, and wind speed records of Bahir Dar meteorological station. The calculated annual average evaporation rate was 1426 mm a −1 .…”

Section: Evaporationmentioning

confidence: 99%

Water Balance for a Tropical Lake in the Volcanic Highlands: Lake Tana, Ethiopia

Alemu

Worqlul²,

Zimale

et al. 2020

Water

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Lakes hold most of the freshwater resources in the world. Safeguarding these in a changing environment is a major challenge. The 3000 km2 Lake Tana in the headwaters of the Blue Nile in Ethiopia is one of these lakes. It is situated in a zone destined for rapid development including hydropower and irrigation. Future lake management requires detailed knowledge of the water balance of Lake Tana. Since previous water balances varied greatly this paper takes a fresh look by calculating the inflow and losses of the lake. To improve the accuracy of the amount of precipitation falling on the lake, two new rainfall stations were installed in 2013. The Climate Hazards Group Infrared Precipitation Version two (CHIRPS-v2) dataset was used to extend the data. After reviewing all the previous studies and together with our measurements, it was found that the period of 1990–1995 likely had the most accurate gauged discharge data. During some months in this period, the lake water balance was negative. Since the river inflow to the lake cannot be negative, water was either lost from the lake via the subsurface through faults, or the outflow measurements were systematically underestimated. Based on the evaporation rate of 1650 mm, we found that unaccounted loss was 0.6 km3 a−1, equivalent to 20 cm of water over the lake area each year. This implies the need for reliable rainfall data and improved river discharge measurements over a greater portion of the basin both entering and exiting the lake. Also, integrated hydrological and geologic investigations are needed for a better understanding of the unaccounted water losses and quantifying the amount of subsurface flow leaving the lake.

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Section: Evaporationmentioning

confidence: 99%

Water Balance for a Tropical Lake in the Volcanic Highlands: Lake Tana, Ethiopia

Alemu

Worqlul²,

Zimale

et al. 2020

Water

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“…This formal data were utilised for comparison and quality checking of the citizen science data and for calculation of potential evapotranspiration (PET) applying the Penman-Monteith FAO56 method [55]. The Penman-Monteith FAO56 method was shown by Adem et al [56] to perform well in the Ethiopian Highlands. The monitoring data were used to assess the seasonality of and relationships between rivers, groundwater, and rainfall and to conduct water balances.…”

Section: Citizen Science Hydrometeorological Monitoring Programmementioning

confidence: 99%

Development of a Hydrogeological Conceptual Model for Shallow Aquifers in the Data Scarce Upper Blue Nile Basin

et al. 2019

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Rural communities in sub-Saharan Africa commonly rely on shallow hand-dug wells and springs; consequently, shallow aquifers are an extremely important water source. Increased utilisation of shallow groundwater could help towards achieving multiple sustainable development goals (SDGs) by positively impacting poverty, hunger, and health. However, these shallow aquifers are little studied and poorly understood, partly due to a paucity of existing hydrogeological information in many regions of sub-Saharan Africa. This study develops a hydrogeological conceptual model for Dangila woreda (district) in Northwest Ethiopia, based on extensive field investigations and implementation of a citizen science programme. Geological and water point surveys revealed a thin (3-18 m) weathered volcanic regolith aquifer overlying very low permeability basalt. Hydrochemistry suggested that deep groundwater within fractured and scoriaceous zones of the basalt is not (or is poorly) connected to shallow groundwater. Isotope analysis and well monitoring indicated shallow groundwater flow paths that are not necessarily coincident with surface water flow paths. Characteristics of the prevalent seasonal floodplains are akin to "dambos" that are well-described in literature for Southern Africa. Pumping tests, recharge assessments, and hydrometeorological analysis indicated the regolith aquifer shows potential for increased utilisation. This research is transferrable to the shallow volcanic regolith aquifers that overlie a substantial proportion of Ethiopia and are prevalent throughout the East African Rift and in several areas elsewhere on the continent. Hydrology 2019, 6, 43 2 of 24Prior to promotion of groundwater irrigation in sub-Saharan Africa, we need to improve our knowledge of the aquifer systems; it is commonly expressed in the literature that the hydrogeology of the region is under-studied and poorly understood [11][12][13]. This view is shared by governments who could provide significant benefit to their populace in the form of interventions with such increased knowledge. For example, the Ethiopia's Ministry of Water Resources stated: "Ethiopia's hydrogeology is complex and at present only partly understood" [14]. The importance of shallow aquifers as locally important water sources is well reported; often simultaneously reported is the scarcity of observations of such groundwater systems, in particular sustained time-series data [11,12,15]. This scarcity of data contributes to poor understanding of these shallow hydrogeological systems. The Ethiopian Agricultural Transformation Agency (ATA) have recognised the importance of shallow aquifers [16] and launched shallow groundwater mapping in 2013 across selected areas in Ethiopia. The mapping is based on acquiring extensive field data of shallow aquifers, remote sensing, and modelling to promote smallholder irrigation.Development of a hydrogeological conceptual model is key to better understanding of a hydrogeological system and is the key first step in any numerical modelling study [...

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“…The elevation of the Ene-Chilala watershed ranges from 1980 to 2404 m. The mean annual precipitation is 1200 mm per year for the last five years and falls mainly between April and October with the greatest amounts of rain in July and August. Potential evaporation during the rain phase is 1-2 mm day −1 and during the dry phase it is between 3 and 5 mm day −1 [28].…”

Section: Description Of the Study Areamentioning

confidence: 99%

Assessment of Practices for Controlling Shallow Valley-Bottom Gullies in the Sub-Humid Ethiopian Highlands

Addisie

Langendoen

Aynalem

et al. 2018

Water

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Abstract:Rehabilitation of large valley bottom gullies in developing countries is hampered by high cost. Stopping head cuts at the time of initiation will prevent large gullies from forming and is affordable. However, research on practices to control shallow gully heads with local materials is limited. The objective of this research was therefore to identify cost-effective shallow gully head stabilization practices. The four-year study was conducted on 14 shallow gullies (<3 m deep) in the central Ethiopian highlands. Six gullies were used as a control. Heads in the remaining eight gullies were regraded to a 1:1 slope. Additional practices implemented were adding either riprap or vegetation or both on the regraded heads and stabilizing the gully bed downstream. Gully heads were enclosed by fencing to prohibit cattle access to the planted vegetation. The median yearly head retreat of the control gullies was 3.6 m a −1 with a maximum of 23 m a −1 . Vegetative treatments without riprap prevented gully incision by trapping sediments but did not stop the upslope retreat. The gully heads protected by riprap did not erode. Regrading the slope and adding riprap was most effective in controlling gully head retreat, and with hay grown on the fenced-in areas around the practice, it was profitable for farmers.

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Predicting Reference Evaporation for the Ethiopian Highlands

Cited by 16 publications

References 26 publications

Water Balance for a Tropical Lake in the Volcanic Highlands: Lake Tana, Ethiopia

Water Balance for a Tropical Lake in the Volcanic Highlands: Lake Tana, Ethiopia

Development of a Hydrogeological Conceptual Model for Shallow Aquifers in the Data Scarce Upper Blue Nile Basin

Assessment of Practices for Controlling Shallow Valley-Bottom Gullies in the Sub-Humid Ethiopian Highlands

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