Abstract:The Northwest Wheat and Range Region is historically known for high soil erosion rates. During the 1920s and 1930s, erosion rates of 200 to 450 t ha -1 (90 to 200 tn ac -1 ) in a single winter season were observed. Improved soil conservation practices over the last 80 years have significantly reduced soil erosion rates, yet there is scarce evidence of significant reductions in sediment loading delivered by streams in the region. In this paper, detailed monitoring data collected in the Paradise Creek watershed, located in the high precipitation zone of the Northwest Wheat and Range Region in north central Idaho, provided an opportunity to assess the impacts of management practices on sediment loading at the watershed outlet. Both detailed event-based sampling over the last eight years and three day per week grab samples collected over the last 28 years indicate a statistically significant decreasing trend in overall sediment load. This decreasing sediment load can be attributed primarily to conversion from conventional tillage systems to minimum tillage and perennial grasses through the Conservation Reserve Program, practices initiated in the late 1970s and early 1980s. Over the last 10 years (1999 to 2009), management practices have targeted gully erosion and stream bank failures. Upstream and downstream sampling shows a larger than expected increase in sediment load through the urban areas of the watershed. Preliminary modeling results and empirical evidence indicate that delayed reduction in sediment load at the watershed outlet and the increased sediment load through the lower urban portion of the watershed may be caused by sediment storage in the stream channel.
Providing useful inflow forecasts of the Manantali dam is critical for zonal consumption and agricultural water supply, power production, flood and drought control and management (Shin et al., Meteorol Appl 27:e1827, 2019). Probabilistic approaches through ensemble forecasting systems are often used to provide more rational and useful hydrological information. This paper aims at implementing an ensemble forecasting system at the Senegal River upper the Manantali dam. Rainfall ensemble is obtained through harmonic analysis and an ARIMA stochastic process. Cyclical errors that are within rainfall cyclical behavior from the stochastic modeling are settled and processed using multivariate statistic tools to dress a rainfall ensemble forecast. The rainfall ensemble is used as input to run the HBV-light to product streamflow ensemble forecasts. A number of 61 forecasted rainfall time series are then used to run already calibrated hydrological model to produce hydrological ensemble forecasts called raw ensemble. In addition, the affine kernel dressing method is applied to the raw ensemble to obtain another ensemble. Both ensembles are evaluated using on the one hand deterministic verifications such the linear correlation, the mean error, the mean absolute error and the root-mean-squared error, and on the other hand, probabilistic scores (Brier score, rank probability score and continuous rank probability score) and diagrams (attribute diagram and relative operating characteristics curve). Results are satisfactory as at deterministic than probabilistic scale, particularly considering reliability, resolution and skill of the systems. For both ensembles, correlation between the averages of the members and corresponding observations is about 0.871. In addition, the dressing method globally improved the performances of ensemble forecasting system. Thus, both schemes system can help decision maker of the Manantali dam in water resources management.
Management of reservoir water resources requires the knowledge of flow inputs in this reservoir. Hydrological rainfall-runoff model is used for this purpose. There are several types of hydrological model according the description of the hydrological processes: black-box models, conceptual models, deterministic physical based model. SWAT is a semi-distributed hydrological model designed for water quality and quantity. This versatile tool has been used all around the world to assess and manage water resources. The main objective of the paper is to calibrate and validate the SWAT model on the watershed of Bafing located between 10˚30' and 12˚30' north latitude and between 12˚30' and 9˚30' west longitude to assess climate change on this river flows. A DEM with a resolution of 12.5 m × 12.5 m, the daily average flows and the daily observed precipitations on the period 1979-1986 (long period) are used as inputs for the calibration, while precipitations for the period 1988-1994 are used for the validation. The sensitivity analysis was done to detect the most determining coefficients during the calibration step. It shows that 19 parameters are required. Then, the effect of the period on the parameters calibration is checked by considering first the whole period of study and then each year of the period of study. The Nash criterion was used to compare the calculated and the observed hygrographs in each case. The results showed that the longer is the period of calibration, the more accurate is the Nash criterion. The calibration per year gave a best Nash criterion except for a single year. During the validation, the parameters calculated on the long period lead to the best Nash criterion. The values of the Nash criterion calibration and validation are very suitable. These results of calibration can be used How to cite this paper:
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