Effects of the floodplain on river discharge into Lake Tana (Ethiopia)

Dessie, Mekete; Verhoest, Niko; Admasu, Teshager; Pauwels, Valentijn R. N.; Poesen, Jean; Adgo, Enyew; Deckers, Jozef; Nyssen, Jan

doi:10.1016/j.jhydrol.2014.08.007

Cited by 53 publications

(50 citation statements)

References 31 publications

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“…4a /sec (equivalent to 10 mm/day). Since rivers are extremely flashy the peak runoff occurs only part of the day and the 6 mm/day observed over the whole day (this paper) is comparable with the 10 mm/day over part of the day (Dessie et al, 2014). The final cause for the "missing" rainfall (i.e., contributing areas not adding up to 1 is that …”

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confidence: 50%

“…2A NSE= 0.77, Table 3) . The fluctuations during the highflow periods in some of the years were not captured which in part is caused by our inability to estimate amounts or rainfall 15 accurately due to the sparse rain gauge network (Dessie et al 2014). There was also an anomaly in the collected data in the fall of 1996.…”

Section: Evaluation Of the Hydrology Modulementioning

confidence: 96%

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Calculating the sediment budget of a tropical lake in the Blue Nile basin: Lake Tana

Zimale

Mogus

Alemu

et al. 2016

Preprint

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Soil erosion decreases soil fertility of the uplands and causes siltation of lakes and reservoirs. However, very little data exists to quantify accurately the impact of sediment on lakes in tropical monsoonal areas in the African highlands. Lake Tana is one of these lakes in Ethiopia. The objective of this study is to quantify the sediment budget for Lake Tana watershed with limited observational data. To overcome these limitations we use the Parameter Efficient Distributed (PED) model that has shown to perform well in the Ethiopian highlands. PED model parameters are calibrated using daily discharge data and 20 sediment concentration infrequently measured for establishing sediment rating curves for the major rivers. The calibrated model parameters are then used to predict the sediment budget for the period 1994-2009. Sediment retained in the lake is calculated from two bathymetric taken 15 years apart and the sediment leaving the lake is based on measured discharge and observed sediment concentrations. Results show that annually on average 34 Mg/ha/year of sediment is removed from the gauged part of the Lake Tana watersheds. Depending on the up scaling method, 14 to 32 Mg/ha/year is transported from the 25 watershed of which 82% to 96% (with the upper estimate more likely) is trapped on the floodplains and in the lake.

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confidence: 50%

Section: Evaluation Of the Hydrology Modulementioning

confidence: 96%

Calculating the sediment budget of a tropical lake in the Blue Nile basin: Lake Tana

Zimale

Mogus

Alemu

et al. 2016

Preprint

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“…The details of SWAT shown in Neitsch et al [58]. It is a semi-distributed continuous widely used hydrological model in the Eastern Nile basins [59,60]. Since the objective of the study was to examine streamflow response to climate change, the land phase of the hydrologic cycle simulated by SWAT is based on the water balance equation: (1) in which SW t is the final soil water content (mm), SW o is the initial soil water content on day i (mm), t is the time (days), R day is the amount of precipitation on day i (mm), Q surf is the amount of surface runoff on day i (mm), E a is the amount of evapotranspiration on day i (mm), W seep is the amount of water entering the vadose zone from the soil profile on day i (mm), and Q gw is the amount of return flow on day i (mm).…”

Section: Overview Of Swatmentioning

confidence: 99%

Optimal Operation of Hydropower Reservoirs under Climate Change: The Case of Tekeze Reservoir, Eastern Nile

Abera

Asfaw

Engida

et al. 2018

Water

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Abstract:Optimal operation of reservoirs is very essential for water resource planning and management, but it is very challenging and complicated when dealing with climate change impacts. The objective of this paper was to assess existing and future hydropower operation at the Tekeze reservoir in the face of climate change. In this study, a calibrated and validated Soil and Water Assessment Tool (SWAT) was used to model runoff inflow into the Tekeze hydropower reservoir under present and future climate scenarios. Inflow to the reservoir was simulated using hydro-climatic data from an ensemble of downscaled climate data based on the Coordinated Regional climate Downscaling Experiment over African domain (CORDEX-Africa) with Coupled Intercomparison Project Phase 5 (CMIP5) simulations under Representative Concentration Pathway (RCP)4.5 and RCP8.5 climate scenarios. Observed and projected inflows to Tekeze hydropower reservoir were used as input to the US Army Corps of Engineer's Reservoir Evaluation System Perspective Reservoir Model (HEC-ResPRM), a reservoir operation model, to optimize hydropower reservoir release, storage and pool level. Results indicated that climate change has a clear impact on reservoir inflow and showed increase in annual and monthly inflow into the reservoir except in dry months from May to June under RCP4.5 and RCP8.5 climate scenarios. HEC-ResPRM optimal operation results showed an increase in Tekeze reservoir power storage potential up to 25% and 30% under RCP4.5 and RCP8.5 climate scenarios, respectively. This implies that Tekeze hydropower production will be affected by climate change. This analysis can be used by water resources planners and mangers to develop reservoir operation techniques considering climate change impact to increase power production.

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“…1b) of their territory are intensively cultivated. The lower floodplains in these catchments with their buffering capacity are not considered by this study, but were discussed by Dessie et al (2014). The Gilgel Abay catchment (Fig.…”

Section: Description Of Study Catchmentsmentioning

confidence: 99%

Analyzing runoff processes through conceptual hydrological modeling in the Upper Blue Nile Basin, Ethiopia

Dessie

Verhoest

Pauwels

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. Understanding runoff processes in a basin is of paramount importance for the effective planning and management of water resources, in particular in data-scarce regions such as the Upper Blue Nile. Hydrological models representing the underlying hydrological processes can predict river discharges from ungauged catchments and allow for an understanding of the rainfall-runoff processes in those catchments. In this paper, such a conceptual process-based hydrological model is developed and applied to the upper Gumara and Gilgel Abay catchments (both located within the Upper Blue Nile Basin, the Lake Tana sub-basin) to study the runoff mechanisms and rainfall-runoff processes in the basin. Topography is considered as a proxy for the variability of most of the catchment characteristics. We divided the catchments into different runoff production areas using topographic criteria. Impermeable surfaces (rock outcrops and hard soil pans, common in the Upper Blue Nile Basin) were considered separately in the conceptual model. Based on model results, it can be inferred that about 65 % of the runoff appears in the form of interflow in the Gumara study catchment, and baseflow constitutes the larger proportion of runoff (44-48 %) in the Gilgel Abay catchment. Direct runoff represents a smaller fraction of the runoff in both catchments (18-19 % for the Gumara, and 20 % for the Gilgel Abay) and most of this direct runoff is generated through infiltration excess runoff mechanism from the impermeable rocks or hard soil pans. The study reveals that the hillslopes are recharge areas (sources of interflow and deep percolation) and direct runoff as saturated excess flow prevails from the flat slope areas. Overall, the model study suggests that identifying the catchments into different runoff production areas based on topography and including the impermeable rocky areas separately in the modeling process mimics the rainfall-runoff process in the Upper Blue Nile Basin well and yields a useful result for operational management of water resources in this data-scarce region.

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Effects of the floodplain on river discharge into Lake Tana (Ethiopia)

Cited by 53 publications

References 31 publications

Calculating the sediment budget of a tropical lake in the Blue Nile basin: Lake Tana

Calculating the sediment budget of a tropical lake in the Blue Nile basin: Lake Tana

Optimal Operation of Hydropower Reservoirs under Climate Change: The Case of Tekeze Reservoir, Eastern Nile

Analyzing runoff processes through conceptual hydrological modeling in the Upper Blue Nile Basin, Ethiopia

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