Establishing Stage–Discharge Rating Curves in Developing Countries: Lake Tana Basin, Ethiopia

A significant constraint in water resource development in developing countries is the lack of accurate river discharge data. Stage–discharge measurements are infrequent, and rating curves are not updated after major storms. Therefore, the objective is to develop accurate stage–discharge rating curves with limited measurements. The Lake Tana basin in the upper reaches of the Blue Nile in the Ethiopian Highlands is typical for the lack of reliable streamflow data in Africa. On average, one stage–discharge measurement per year is available for the 21 gaging stations over 60 years or less. To obtain accurate and unique stage–discharge curves, the discharge was expressed as a function of the water level and a time-dependent offset from zero. The offset was expressed as polynomial functions of time (up to order 4). The rating curve constants and the coefficients for the polynomial were found by minimizing the errors between observed and predicted fluxes for the available stage–discharge data. It resulted in unique rating curves with R2 > 0.85 for the four main rivers. One of the river bottoms of the alluvial channels increased in height by up to 3 m in 60 years. In the upland channels, most offsets changed by less than 50 cm. The unique rating curves that account for temporal riverbed changes can aid civil engineers in the design of reservoirs, water managers in improving reservoir management, programmers in calibration and validation of hydrology models and scientists in ecological research.

Investigation of spillway rating curve via theoretical formula, laboratory experiment, and 3D numerical modeling: A case study of the Riam Kiwa Dam, Indonesia

The spillway rating curve of the Riam Kiwa Dam was investigated via theoretical formula, laboratory experiment, and 3D numerical modeling. It is an ogee type with two uncontrolled and five gated spillways with a total length of 77.5 m. The experiment was performed with a scale of 1:50, while the numerical modeling was conducted using FLOW-3D software. Several discharge values (16.67–2,652.7 m3/s) were tested and observed for two different scenarios of gate openings. For the low discharge in Scenario 1, the theoretical formula and FLOW-3D computed the rating curve less accurately with the error values greater than 10%. A similar phenomenon was observed in Scenario 2, where both theoretical formula and FLOW-3D predicted the rating curve accurately with error values less than 10% for the higher discharge. The discharges tend to be overestimated for the water depth values greater than 2 m giving the average discharge deviation of 6% for the PMF condition. FLOW-3D was found to calculate water depth for all scenarios accurately. It shows a promising approach between numerical simulation and physical modeling, to minimize laboratory model construction costs.

Sediment Yield and Reservoir Sedimentation in Highly Dynamic Watersheds: The Case of Koga Reservoir, Ethiopia

Soil erosion is exacerbated by unsustainable land-use activities and poor management practices, undermining reservoir storage capacity. To this effect, appropriate estimation of sediment would help to adopt sustainable land-use activities and best management practices that lead to efficient reservoir operations. This paper aims to investigate the spatial variability of sediment yield, amount of sediment delivery into the reservoir, and reservoir sedimentation in the Koga Reservoir using the Soil and Water Assessment Tool (SWAT). Sediment yield and the amount entered into the reservoir were also estimated using a rating curve, providing an alternative approach to spatially referenced SWAT generated suspended sediment load. SWAT was calibrated from 1991 to 2000 and validated from 2002 to 2007 using monthly observations. Model performance indicators showed acceptable values using Nash-Sutcliffe efficiency (NSE) correlation coefficient (R2), and percent bias (PBIAS) for flow (NSE = 0.75, R2 = 0.78, and PBIAS = 11.83%). There was also good agreement between measured and simulated sediment yields, with NSE, R2, and PBIAS validation values of 0.80, 0.79, and 6.4%, respectively. The measured rating curve and SWAT predictions showed comparable mean annual sediment values of 62,610.08 ton/yr and 58,012.87 ton/yr, respectively. This study provides an implication for the extent of management interventions required to meet sediment load targets to a receiving reservoir, providing a better understanding of catchment processes and responses to anthropogenic and natural stressors in mixed land use temperate climate catchments. Findings would benefit policymakers towards land and water management decisions and serve as a prototype for other catchments where management interventions may be implemented. Specifically, validating SWAT for the Koga Reservoir is a first step to support policymakers, who are faced with implementing land and water management decisions.

Study on the Contribution of Normalization to Reducing Flood Risk in the Ciliwung River, Tebet District, Jakarta

Jakarta is the capital city of the State of Indonesia and fast economy and population growth rate. With these, urbanization continues to increase every year. In this study, we analyse the effect of river normalization on reducing flood risk on the MT. Haryono - Manggarai section based on the Hec-RAS hydraulic model. Boundary Condition applied in upstream river is flow hydrograph with a peak discharge of 561.48 m3/s. In the upstream part, a rating curve is applied from the water level measurement data for the Manggarai Sluice Gate. While in the middle, the lateral flow from the urban drainage channels is inserted. The simulation results show that normalizing the channel can increase the drainage capacity as implied by the decrease in the flood water level. However, downstream there is backwater due to the lack of capacity of the Manggarai floodgate.

Application of Stage-Fall-Discharge Rating Curves to a Reservoir Based on Acoustic Doppler Velocity Meter Measurement Data

The applicability of the stage-fall-discharge (SFD) method in combination with acoustic Doppler velocity meter (ADVM) data, upstream of a hydraulic structure, specifically, the Sejong-weir located in the Geum River, Korea, was examined. We developed three rating curves: a conventional simple rating curve with the data measured using an acoustic Doppler current profiler (ADCP) and floating objects, an SFD rating curve with the data measured using the ADCP and floating objects, and an SFD rating curve with the data measured using an ADVM. Because of the gate operation effect, every rating curve involved many uncertainties under 1000 m3/s (3.13 m2/s, specific discharge). In terms of the hydrograph reconstruction, compared with the conventional simple rating curve, the SFD developed using ADVM data exhibited a higher agreement with the measured data in terms of the pattern. Furthermore, the measured discharge over 1000 m3/s primarily ranged between 97.5% and 2.5% in the graph comparing the ratio of the median and observed discharge. Based on this experiment, it is confirmed that the SFD rating curve with data to represent the backwater effect, such as ADVM data, can reduce the uncertainties induced by the typical rating curve

CAMELS-AUS: hydrometeorological time series and landscape attributes for 222 catchments in Australia

This paper presents the Australian edition of the Catchment Attributes and Meteorology for Large-sample Studies (CAMELS) series of datasets. CAMELS-AUS (Australia) comprises data for 222 unregulated catchments, combining hydrometeorological time series (streamflow and 18 climatic variables) with 134 attributes related to geology, soil, topography, land cover, anthropogenic influence and hydroclimatology. The CAMELS-AUS catchments have been monitored for decades (more than 85 % have streamflow records longer than 40 years) and are relatively free of large-scale changes, such as significant changes in land use. Rating curve uncertainty estimates are provided for most (75 %) of the catchments, and multiple atmospheric datasets are included, offering insights into forcing uncertainty. This dataset allows users globally to freely access catchment data drawn from Australia's unique hydroclimatology, particularly notable for its large interannual variability. Combined with arid catchment data from the CAMELS datasets for the USA and Chile, CAMELS-AUS constitutes an unprecedented resource for the study of arid-zone hydrology. CAMELS-AUS is freely downloadable from https://doi.org/10.1594/PANGAEA.921850 (Fowler et al., 2020a).

Kajian Hidrolika Sungai Kusan Kabupaten Tanah Bumbu Provinsi Kalimantan Selatan Dengan Uji Model Fisik dengan Skala Distorsi Vertikal 1:40 Horizontal 1:80

Penelitian tersebut dilakukan untuk mengetahui kondisi hidrolika di Sungai Kusan secara prototype yang dimodelkan yang nantinya dibandingan dengan hasil perhitungan teori. Dengan debit pengujian dilakukan menggunakan rating curve pada sungai model Sungai Kusan dengan skala distorsi vertical 1:40 horisontal 1:80. Diperlukan pengujian terhadap bebeara sampel sedimen yang bertujuan untuk menentukan sedimen yang nantinya akan digunakan saat pengujian model sungai. Terdapat 5 sampel yang diujikan, dengan perbandingan jumlah pasir dan jumlah batu bara 1:9, 2:8, 3:7, 4:6 dan 5:5, mengacu pada perbandingan 3:7 sebagai kriteria yang paling baik. Estimasi debit yang lewat pada kondisi eksisting adalah dengan perhitungan lengkung debit pada beberapa section Sungai Kusan dengan menggunakan slope 0,007007 (slope rerata) dan n manning 0,03. Dari liku debit ditentukan debit yang digunakan adalah debit kecil dengan ketinggian air ± 0,50 m (14,29 m3 /detik), debit sedang dengan ketinggian air ± 2,00 m (156,07 m3 /detik) dan debit besar dengan ketinggian air ± 3,50 m (519,64 m3 /detik).