GeoScience Engineering

The Assessment of Heavy Metals Pollution in the Nyabarongo River Sediments – Case Study: Mageragere Sector

Cedrick NSENGIYUMVA — 2023-12-22

The accumulation of heavy metals in rivers’ sediments near industrial wastes and mining activities has been a serious issue in developing countries including Rwanda and it has caused different environmental impacts on aquatic and terrestrial lives. Environmental studies have reported heavy metals pollution (lead, manganese, copper, zinc, nickel, iron, and cadmium) in major Rwandese rivers such as Mpazi, Rusine, and Nyabugogo. The increase in heavy metal concentrations in the environment results in abnormal enrichment, which in turn, affects the surrounding environment. This study aimed to investigate the heavy metals in Nyabarongo sediments, Mageragere sector using both X-ray fluorescence (XRF) and Atomic Absorption Spectrometer (AAS) instruments. Sediments samples were collected systematically on four sampling stations and the results showed that the Cadmium (Cd), Lead (Pb), and Manganese (Mn) concentrations among the investigated heavy metals are above the Rwanda Standard Board (RSB) and World Health Organization (WHO) guidelines for soils and sediments, meaning that those metals are the measure pollutants in the sediments of Nyabarongo River and the study has recommended the people around the river to reinforce the erosion control measures and not to use Nyabarongo water for domestic use and animal farming activities because of the concentration of heavy metals it contains that are toxic to animals, plants and micro-organisms.

Keywords: Heavy metals; Nyabarongo River; Pollution; River sediments; World Health Organization (WHO).

Sediment Transport Modeling at the Oued Fodda Watershed Level Using HEC-RAS 1D Software

Souhila BENKACI — 2023-12-22

The objective of the current work is to determine the amount of sediments transported upstream and at the ‎level of Oued Fodda dam. The latter is considered one of the first large dams built in Algeria. It’s ‎exposed to a serious siltation problem that ‎reduces its capacity every year. The simulation was executed ‎using the HEC-RAS software, for the period varied from January 01, 2016 to April 30, 2016. The ‎modeled section consisted of about 9999 m length, subdivided into 141 river stations distant from each ‎other by 70 m. The ‎observation of the studied river section bed- profile was selected as a criterion ‎for ‎comparing the results of the model with the real values observed. A roughness ‎coefficient of 0.031 ‎was used. A quantitative estimate with a determination coefficient, R2, of 0.92 was used to support the ‎validity‎. The mass and concentration of sediments increased significantly in the cross-sections ‎located ‎at ‎the dam upstream.‎ A total cumulative mass was estimated at approximately 712699 tons, just upstream of ‎the dyke, and a maximum concentration of 22.35 g/l was observed, particularly for three main sections ‎selected upstream of the Fodda wadi. However, at the reservoir level, the concentration variability is ‎observed during flood periods, i.e., only for the most important flows.‎

Keywords: GIS; HEC-RAS; Oued Fodda dam; Sediment transport; Siltation.

Effect of Changing Jaw Crusher Parameters on Granulometry and Static Angle of Repose of Crushed Aggregate

Martin ŽÍDEK — 2023-12-22

Crushing is one of the important technological operations in the reduction of oversized pieces of utility material. It is of great importance in mineral processing, where the excavated material is processed into a final product or for the purpose of further treatment. There are several different types of industrial crushers. In practice, it is usually not possible to process the raw material into the desired product using only one machine; it is usually necessary to use several crushers, often in combination of two or more construction types. When the material is crushed, its grain composition and flow properties change. The change in these properties affects the way the material is handled, in particular its transport and storage. A systematic approach to the influence of crusher parameter settings on the flowability and granulometry of the resulting product has not yet been published. In this study, the effect of laboratory jaw crusher parameter settings on the granulometry and static angle of repose of different types of crushed aggregates was investigated. It was observed that changing the setting of the crusher gap width changes the ratio of dust and coarser particles of the crushed material, and this ratio has a significant effect on the changes in the static angle of repose of this material.

Keywords: Angle of repose; Comminution; Crushing; Granulometry; Jaw crusher.

Trend Assessment by the Mann-Kendall Test and the Innovative Trend Analysis Method (North-West Algeria)

Oumeria OUFRIGH — 2023-12-22

In this article, a trend study, in two watersheds Coastal-Oran and Macta (North-West of Algeria), is carried out using monthly and seasonal rainfall during the period 1975–2015 at 38 stations. Mann-Kendall (MK) and Innovative Trend Analysis (ITA) methods are applied comparatively. The aim of this study is to verify if the trend detection ability is the same in both methods. Monthly rainfall analysis by the MK test shows that 82% of the stations have no significant trends. In contrast, the ITA method detects positive (negative) trends in 56% (33%) of stations in the low rainfall component, 53% (40%) in the average and 41% (58%) in the high rainfall. On a seasonal scale, the MK test still not aware of trends in 75% of the studied stations, while the ITA shows that 63% (31%) of stations with increasing (decreasing) trends. Studying the rainfall trend, using the ITA and Mann-Kendall methods, in the same area can help to understand past variations and therefore extrapolate the results to other areas with the same climate. This is a crucial step in managing climate-related issues. In addition, the ITA detects hidden sub-trends in the low, medium and high components that the MK test does not, which shows the superiority of the ITA method over MK method.

Keywords: Hidden trend; ITA; Mann-Kendall; North-West Algeria; Rainfall.

Determination of Rock Parameters Used for Calibration of Constitutive Model

Marek BRABEC — 2023-12-22

Mathematical modeling is an important part of designing underground and other structures. However, the accuracy of the obtained results is strongly dependent on the input parameters quality of the selected material (constitutive) model. An insight into this issue is outlined in this article. Special emphasis was placed on various possibilities of laboratory determination of the necessary parameters for calibration of the Mohr-Coulomb and Hoek-Brown constitutive models. Described procedure was also applied to a selected rock type – Čeřínek-type granite of the Moldanubian pluton, a candidate rock in which a deep geological repository for used nuclear fuel and high-level radioactive nuclear waste might be built in a future.

Keywords: Constitutive model; Granite; Hoek-Brown; Mathematical modelling; Mohr-Coulomb.

The Use of the HEC-HMS Model to Improve Regionalized Hydrological Modeling and Its Application to the Cheliff Basin, Algeria

Noureddine MAKHLOUFI — 2023-12-22

Hydrological modeling is an effective tool for predicting the hydrological response of watersheds in order to develop appropriate water resource management strategies. Various modeling techniques are available to simulate rainfall-runoff processes in ungauged basins, including regionalization of hydrologic model parameters. Regionalization by spatial proximity (SP) and physical similarity (PS) were chosen for this study to be used with Hydrologic Modeling System (HEC-HMS), which is semi-distributed hydrological model, to evaluate the performance of the model in simulating sub-basin flows as well as the applicability of averaging methods in the case of ungauged sub-basins. Eight sub-basins belonging to the large Cheliff watershed were selected using available data from the period 2007 to 2012. In order to perform a controlled regionalization, one of the eight sub-basins (Wadi Tikzal) was assumed to be ungauged, and five sub-basins were selected to be donors by the (SP) regionalization method and five others by the (PS) regionalization. The results were compared to the original gauged sub-basin series. The performance analysis was carried out through the Nash-Sutclife Efficiency (NSE), the coefficient of determination (R²) and the root mean squared error (RMSE). The results of the simulation are generally satisfactory for wadi Tikzal sub-basin. The model adequately simulated the flows in the other sub-basins, during both calibration and validation phases. The results obtained showed that the regionalization methods used in this study, with the arithmetic mean and the inverse distance weighting (IDW), yielded good results with NSE and R² values exceeding 0.75 and RMSE values were close to 0.20. The arithmetic mean gave higher results compared to the IDW method, the mean of NSE between the two methods is 0.68 for the arithmetic mean and 0.65 for IDW, and R² of 0.69 for the arithmetic mean and 0.65 for IDW. The obtained results demonstrate that the regionalization by spatial proximity and physical similarity, using the HEC-HMS hydrological model can be effectively used to predict streamflow in ungauged watersheds, leading to effective water resources management, which enriches the literature regarding the flows regionalization, averaging methods and HEC-HMS performance, in ungauged sub-basins and especially in the northern Algerian region.

Keywords: Arithmetic mean; Cheliff basin; HEC-HMS; Inverse distance weighting; Physical similarity; Regionalization; Spatial proximity.