Sub-basin Area Research Articles

Groundwater hydro-geochemistry, irrigation and drinking quality, and source apportionment in the intensively cultivated area of Sutlej sub-basin of main Indus basin

Groundwater hydro-geochemistry, irrigation and drinking quality, and source apportionment in the intensively cultivated area of Sutlej sub-basin of main Indus basin

EVALUATION OF VULNERABILITY TO SOIL LOSS IN THE ESPINHO STREAM SUB-BASIN, MUNICIPALITY OF MORRINHOS, CEARÁ, BRAZIL

The present work aims to identify the different degrees of vulnerability to soil loss in the Espinho stream sub-basin, municipality of Morrinhos, Ceará, Brazil. For this, it was used as a methodology the construction of a geographic database with the help of the QGIS software version 3.16-Hanover, from the criteria Geology (G), Slope (D), Pedology (S), Use and Coverage (U ) and Climate (C). Four classes of vulnerability to erosive processes were identified in the sub-basin. The results showed that the classes with predominance of pedogenetic processes accounted for 34% of the sub-basin area. The one whose processes represent balance between pedogenesis and morphogenesis was 64%. The class where morphogenetic processes prevail totaled 2% of the studied area.

Dynamic Variation in Vegetation Cover and Its Influencing Factor Detection in the Yangtze River Basin from 2000 to 2020

Studies on the dynamic variation in vegetation cover and detecting its influencing factors are highly valuable for monitoring regional ecological environment quality and evaluating forestry restoration project effects. In this study, on the basis of the MODIS normalized difference vegetation index (NDVI), in situ climate data, digital elevation model, population density, nighttime lights using Theil-Sen Median analysis, Mann-Kendall significance test, stability analysis, and geographical detector model, the spatiotemporal variation and stability of vegetation cover in the context of multi-spatiotemporal scales were analyzed, and the dominant influencing factors that affect the spatial differentiation of vegetation cover were further detected. The results showed that the vegetation cover showed a fluctuant increasing trend, and the changing trend exhibited obvious spatial heterogeneity with the increasing rate being higher in the middle and lower in the east and west portion of the Yangtze River basin from 2000 to 2020. At the sub-basin scale, except for that in the Taihu Lake basin, the vegetation cover in all sub-basin units exhibited an increasing trend during the study period. The areas with an increasing trend accounted for 84.09% of the study area, in which the areas with extremely significant increases and significant increases accounted for 53.67%, which were mainly distributed in the Wujiang River basin, Yibin-yichang, Jialing River basin, Han River basin, and Dongting Lake basin. The vegetation cover showed lower stability in the upper reaches of the Jinsha-shigu River basin and Taihu Lake basin and higher stability in other sub-basin units of the study area. Elevation was an important factor affecting the vegetation variation in all sub-basin areas. Climatic factors presented the highest impact on vegetation variation in the upper reaches of the Jinsha-shigu River basin, and human activities exhibited the greatest impact on vegetation variation in the Wujiang River basin, lower reaches of Hukou basin, and Taihu Lake basin. The interaction of the two influencing factors on vegetation variation showed mutual and non-linear enhancement, and the interaction between elevation and wind speed presented the highest value, with an explanatory power of 68%. The ecological exploration results showed that human activities combined with topographic factors and climate factors, except for slope and relative humidity, significantly differed in the explanatory power of vegetation variation in the Yangtze River basin. These results can provide a basis for formulating comprehensive vegetation resource management in the Yangtze River basin that takes into account regional climate, topography, and human activities.

Estimation of annual rate and spatial distribution of soil erosion in the Jamuna basin using RUSLE model: A geospatial approach

Soil erosion poses a serious threat to the western Jamuna sub-basin area in Bangladesh, comprising of 8 districts and 202 unions. The Revised Universal Soil Loss Equation (RUSLE) methodology integrated with Remote Sensing and Geographic Information System (GIS) was applied to compute the annual soil erosion rate for the western Jamuna sub-basin area. Primarily open-source data was utilized in this study to propose a low-cost and rapid soil erosion monitoring framework. Results indicate that a total of 598,232 tons of soil is being lost annually from the study area. Furthermore, the study estimates a potential average soil erosion rate of approximately 29.5 tons/ha/year in the 202 unions. The spatial distribution of soil erosion suggests that the unions of Bogra, Sirajganj and Jamalpur districts undergo higher soil loss compared to the unions of Pabna and Natore districts. The three unions with dominant mean soil erosion rates are the Bhandarbari and the Sariakandi Paurashava of Bogra district, and the Kaoakola union of the Sirajganj district. Heavy rainfall after a prolonged dry season, the presence of steep slopes and the susceptibility of the unions located in proximity to the Bangali river and the Jamuna river leading to higher rates of surface runoff and floods resulted in higher rates of soil erosion. On the contrary, the Atgharia Paurashava and Debottar unions of Pabna district and the Moshinda union of Natore district are the unions with minimal soil erosion rates, which likely be attributed to the presence of flat terrain, low annual rainfall, higher vegetation cover and the predominance of clayey soils. Overall, the study identifies an increasing trend of soil erosion rates from the south-western part of the study area towards the central, north-eastern and south-eastern parts which are close to the Jamuna river. Such quantification of annual soil loss is necessary for the formulation and implementation of effective soil conservation strategies.

Estimation of erosion and deposition by Unit Stream Power Erosion and Deposition in a sub-basin on the Mogi Guaçu River’s margins, municipality of Mogi Guaçu, SP, Brazil

Information regarding the soil erosive processes that comprise the detachment, transport and deposition, are essential when analyzing hydrological processes associated with the generation of the flow in the landscape and water recharge. The USPED (Unit Stream Power Erosion and Deposition) model has been applied in several regions around the world for providing more accurate estimates, since it adds a physical base that relates the relief morphology with the erosion-defining runoff parameters. The current study aims to analyze erosion and deposition using the USPED model in a sub-basin on Mogi Guaçu River’s margins, municipality of Mogi Guaçu, SP, Brazil, and generate subsidies for future diagnoses regarding areas in the region with greatercapacity for water storage, based on less erosion. The loss of mineral and organic particles arising from the erosive process changes the soil’s effective depth, texture and structure, directly and negatively impacting its capacity to absorb and retain water. 60% of the sub-basin’s area was unaffected by considerable processes of erosion and deposition, both due to the current arboreal vegetation, but also the smooth relief of the site. The erosion and deposition sites have totaled 23.42 and 15.76% of the sub-basin area respectively, being adjacent to one another and preferably near or within the drainage network. The results of the spatialization were validated by the Kappa Index and revealed that the UPSED model obtained an excellent agreement with the “ground truth”. Stability in terms of erosion, favors the water recharge in area, since the soils present a sandy texture and in addition, the Latossolos, which make up 63% of the sub-basin, are deep and possess a high water storage...

Interaction between volcanic and non-volcanic systems and its implication for prospectivity in the Faroe–Shetland Basin, NE Atlantic continental margin

Exploration in the Faroe–Shetland Basin on the Faroese Continental Shelf has revealed thick and complex volcanic successions and discovery of inter-volcanic oil-bearing siliciclastic sandstone fan deposits in the central parts of the basin. The possibility for such play types at the fringe of the North Atlantic Igneous Province requires a better understanding of the interaction between competing sedimentary and volcanic depositional transport systems. We have re-examined volcanic units in cuttings from exploration wells in the greater Judd Sub-basin area for evaluation of facies and geochemical affinity. This allows for chemostratigraphical correlation of wells to the absolute radiometrically age-constrained Faroe Islands Basalt Group. The collective well data were subsequently tied to a regional interpretation of 2D seismic data which facilitated a detailed interpretation of temporal development of the volcanic successions in the Judd Sub-basin area in terms of geometry, volcanic facies, depositional environment, and interdigitation with non-volcanic sedimentary units. The Judd Sub-basin was influenced by major volcanic phases during pre-breakup and syn-breakup. The influence was both direct, in the form of volcanic deposits, and indirect, in the form of obstructing established sedimentary transport systems and creating new provenance areas. The volcanic transport systems reached different areas of the Judd Sub-basin at different times during pre-breakup volcanism. The earliest incursion in the west was during late Mid Paleocene (T-sequence T31/T32). With at least three stratigraphically discrete incursions of volcanic material into the Judd Sub-basin, possibilities arise for sub- and inter-volcanic stratigraphic and structural traps for each incursion.

Soil erodibility assessment of laterite dominant sub-basin watersheds in the humid tropical region of India

Sub-basin prioritization is an essential aspect of watershed development initiatives as a part of the sustainable management program for natural resources. The present work aims to analyse the soil erodibility at sub-basin scale in the Pathro River Basin area of Jharkhand, India. Degradation of land resources is multifaceted, and its severity leads to soil detachment, thus rendering it a complex and interlinked system. Sixteen closely correlated morphometric attributes of the erosion process are considered for prioritizing watersheds by applying the frequency ratio (FR) method. This work assigns Support Vector Machine (SVM) algorithm to evaluate the existing soil risk condition with the help of twelve soil erosion influencing geo-environmental factors at the sub-basin area. Soil samples were examined using scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX) to acquire the micro-graphic and physical condition of dominant soil forming minerals and their influences to develop susceptibility of peds to erode. The prioritisation results from both approaches show a reasonably similar output, identifying nine sub-watersheds as very high soil erosion-prone, while four sub-watersheds are recognised as low-risk. Field observation reveals that lowering of plunge pool and head retreat are dominant processes of gully extension in very high to high sub-basin prioritization areas. The final output provides a comprehensive platform for the urgency of policy interventions to minimize erosion risk and ecological damage in prioritized areas of Pathro River Basin, Jharkhand.

A balanced watershed decomposition method for rain-on-grid simulations in HEC-RAS

Abstract Rain-on-grid simulations for the modeling of 2D unsteady flows in response to precipitation input are implemented in Hydrologic Engineering Center's River Analysis System (HEC-RAS) software by means of a finite volume method and a sparse parallel linear solver running on a unique processor. Obviously, this may fail due to memory shortage when the discretization yields too large linear systems. Such simulations are good candidates for the design of partition and domain decomposition methods for the modeling of very large catchments by means of hydrological sub-units. Thinking in load-balanced computations, the proposed area-balanced partition method is based on the flow accumulation information. Implemented in HEC-RAS, the domain decomposition method comprises 2D–1D models combining 2D sub-unit meshes to 1D channels for extracting outflow data from upstream units and passing the information to downstream units. The workflow is automated using the HEC-RAS Controller. As a case study, we consider the French Saar catchment (1,747 km2). The new partition methods demonstrate a better equilibrium for sub-basin areas and the computational load for the sub-problems. The total computational time is substantially reduced. Domain decomposition is required for carrying rain-on-grid simulations over the Saar watershed (2,800,000 elements). The resulting discharge and flood maps show very good agreements with available data.

Mapping Potential Zones for Groundwater Recharge Using a GIS Technique in the Lower Khwae Hanuman Sub-Basin Area, Prachin Buri Province, Thailand

The lower Khwae Hanuman sub-basin in Thailand suffers from water shortage during each dry season. As such, groundwater resources are an additional freshwater source in this region, in particular for cultivating activities. Thus, an understanding of the volume of groundwater recharge into the saturated zone is required. The objective of the study is to assess the groundwater recharge potential (GRP) using the weighted overlay analysis method by geographic information system (GIS) and finally checking the reliability of GRP map using observed specific capacity carried out by the Department of Groundwater Resources (DGR). The geological and hydrogeological features that affect groundwater potential are the lithology, land use, lineaments, drainage, slope, and soil. The weighting and rating of these six influencing factors were determined by assessing the interrelationship of the main and minor influences of each factor based on several literature reviews, followed by a weighted overlay analysis with GIS, in association with groundwater recharge. The GRP can be classified in descending order: high, moderate, low, and very low, where about 33.9 km2 (2.26% of the total area of 1,500 km2) had high recharge potentiality, located at the center of the area. Only 12.8% of the total precipitation (271.75 million m3/y or approximately 181.2 mm) infiltrated the groundwater aquifer, while the rest was lost by either surface runoff or evapotranspiration. Based on GRP sensitivity analysis index, lithology was the most efficient influencing factor in GRP mapping. Most groundwater wells (>96% or 369 wells) were classified into the classes of low and moderated, which agree to the GRP zones. The results of calculating the area under the curve (AUC) of the receiver operating characteristic (ROC) curve were 86.0 percent, with relatively good predictive accuracy. The stable baseflow analysis would be used to confirm the amount of GRP by weighting overlay technique. Therefore, the GRP method can be applied in other areas, particular in similar hydrogeological characteristics. The first-hand recharge potential map and groundwater recharge information in this area can be used to establish an effective groundwater exploration program for agricultural activities; it is also used to appropriate sustainable yields from each groundwater basin to provide groundwater over the long-term, without negatively impacting the environment and without affecting the groundwater balance as it has recharge in the rainy seasons, which can use groundwater sustainably. It is in line with the sustainable development goals (SDGs) in goal number six of the UN.

Evaluation of groundwater quality for drinking and irrigation purposes using GIS-based water quality index in urban area of Abaya-Chemo sub-basin of Great Rift Valley, Ethiopia

Groundwater is the major resource for drinking and irrigation purposes in urban areas of Abaya-Chemo sub-basin of Great Rift Valley, Ethiopia. There is an incredible increase in demand in the sub-basin for good-quality groundwater resources. However, the exhaustive irrigation and rapid urbanization has posed a serious threat to groundwater quality in the urban districts of sub-basin like Arba Minch town. The aim of the study was to evaluate the groundwater quality status and to map their spatial distribution with respect to the suitability for drinking and irrigation purposes in Arba Minch town, Ethiopia. Fourteen bore well samples were examined for geochemical variations and groundwater qualities. The spatial distribution maps of quality parameters were prepared using the kriging method in ArcGIS 10.3. Drinking water quality index, sodium adsorption ratio (SAR), percentage sodium (Na%), residual sodium carbonate (RSC), and permeability index (PI) were considered for drinking and irrigation suitability assessment. Comparison of the hydrochemical results with the World Health Organization (WHO) and Ethiopian drinking water standards (ES) and various classifications revealed that the current status of the groundwaters is suitable for drinking and irrigation purposes except for a few sites at the northwestern part of the study area. The WQI results revealed that 7% and 64% of samples fall from excellent to good classes for drinking categories. Irrigation indices also demonstrated that 80% of samples fall in good classes for irrigation purposes. About 75 percent of samples belong to Ca–Mg-HCO3 facies, and the reaming samples belong to Ca–Mg–Cl facies. The results of the study concluded that the proposed approach is reliable and efficient for the groundwater pollution status evaluation and can also be applied in decision making for effective groundwater resources monitoring in the study area.

The Climate Challenge in Managing Water: Evidence Based on Projections in the Mahanadi River Basin, India

This study analyzes the long-term changes in the rainfall and surface hydrology of the upper and middle sub-basins of Mahanadi, an inter-state river basin in eastern India that experiences climate-induced hydrological extremes, and draws implications for the sustainability of irrigation and drinking water supplies. The likely impacts of rainfall changes on surface flow were also modeled. A Water Evaluation and Planning (WEAP) model was set up (beginning June 2009 and ending May 2050) to analyze the future water balance of the basin for the expected changes in socio-economic conditions. The model was also run for future scenarios that considered different water management interventions, and hydrological consequences of climate variability and change. The model results showed that there would be a water deficit, about 2,182 million cubic meters (MCM) by 2050 (20% of the demand) even under the business-as-usual scenario. The gap is expected to widen to 5,005 MCM (25% of the demand) under a high growth scenario. Further, the water demand management interventions in agriculture would be able to reduce the overall demand for water in the basin to some extent, while it would also reduce the supplies slightly due to a reduction in return flows occurring as a result of irrigation efficiency improvement. The water deficit under this scenario will reduce to about 2,773 MCM in 2050. Under the predicted changes in climate, the water deficit is expected to reduce further (will be 1,684–2,373 MCM in 2050) due to an increase in supplies owing to an increase in the catchment yields resulting from higher rainfall. While there will be a significant amount of outflow from the two sub-basins in all the scenarios in most future years (ranging from 25,286 MCM to 28,697 MCM in 2050), during drought years, the water deficit in the upper basin areas will increase slightly, but with a significant reduction in the outflows to the lower sub-basin areas by 2046–47 (will be about 11,311 MCM). These results indicate that there is a need for building more water storage/diversion infrastructure to detain floodwaters during wet years that can provide buffer storage for the dry years.

Intelligent estimation of the discharge peak in Al Aqiq drainage basin: A case study in Al Madinah Munwwarah region

The NRCS-CN model is one of the commonly used models for the estimation of discharge peak in a watershed in Saudi Arabia using the DEM outputs and daily rainfall data. The current study aims to classify the sub-basins using rainfall volume, rain off volume and estimate the discharge peak using NRCS-CN method. The drainage map of the studied sub-basin areas was extracted from SRTM Dem 30 m outputs. To estimate the surface runoff and its discharge peak, the drainage area was divided into four tributary basins for Wadi Al-Aqiq using the WMS software outputs from SRTM Dem 30 m. The extracted subbasins were Wadis Rim, Al Yitimah, Al Ishsh and Sha'ib Ruwawah. The results indicate the importance of the integrated use of the digital processing outputs of the DEM in extracting the morphometric variables necessary in calculating the concentrationtime, unit peak discharge and the land resources map in determining the runoff curve. In addition, the weighted curve numbers were ranged between 88.4, 89.9, and 92.1 in Wadi Al Ishsh, wadi Rim, and wadi Al Aqiq watersheds, respectively. It was evident that the attained results can be calibrated by the actual recorded discharge and related to several watersheds.

Evaluación del índice de pobreza hídrica (WPI) en la cuenca de Borujerd-Dorood (Irán) para reforzar los planes de gestión del territorio

El Índice de Pobreza Hídrica (WPI) se considera, en general, una herramienta simple y clara para evaluar los efectos de factores combinados sobre la escasez de agua y la tensión de los recursos hídricos. En esta investigación, intentamos centrarnos en las problemáticas hídricas en las cabeceras de montaña de la cuenca de Karoon en Irán para analizar el estado de los recursos hídricos. Para este propósito, los datos requeridos se obtuvieron en primer lugar mediante la preparación de un informe de la Autoridad del Agua, la parte Agrícola y la Organización de Agua y Saneamiento del Condado de Borujerd. Luego, se estimó el valor del WPI a escala de subcuenca del río Karoon considerando como recurso la posibilidad de acceso, capacidad socioeconómica, usos y criterios de calidad ambiental. Los resultados de esta investigación indicaron un rango de variación entre 6,6 y 18,2, obteniendo el punto más bajo por su condición ambiental actual y el punto más alto por el fácil acceso. Los valores más altos de cada criterio muestran las mejores condiciones que conducen a una menor pobreza hídrica en esa subcuenca. En general, el valor de WPI es aproximadamente 67,65, según la clasificación del centro de Ecología e Hidrología de Wallingford, esta subcuenca se ubica en un rango de pobreza hídrica de baja a moderada. Dado el carácter multidimensional del WPI y considerando todos los factores que afectan a la disponibilidad o falta de recursos hídricos, así como las implicaciones económicas y sociales para la población dedicada, principalmente a la agricultura y la ganadería, podemos concluir que este índice puede ser considerado como una herramienta útil para esta región priorizar las áreas críticas y un paso efectivo para el desarrollo y uso óptimo de sus recursos hídricos.

Benthic redox conditions and nutrient dynamics in the ca. 2.1 Ga Franceville sub-basin

The co-existence of motile macroorganisms and mat-building cyanobacteria in the Paleoproterozoic FB2 Member of the Franceville sub-basin, Gabon, points to the possible emergence of multi-trophic-level biological interaction by 2.1 billion years (Ga) ago. However, it is uncertain how these shallow-marine communities acquired and cycled nitrogen, a key, biolimiting nutrient required to sustain life at all trophic levels. Here, we use carbon and nitrogen isotope data from ancient microbial mats and host sediments, in combination with bottom-water redox proxies, to constrain biogeochemical processes operating in these settings. In this shallow-marine upwelling zone, iron speciation data and redox-sensitive metal concentrations point to oxygen-deficient bottom waters, which were episodically renewed with upwelling deep anoxic waters rich in nutrients and manganese. Organic carbon and nitrogen isotopes show little difference between the mat-related structures (MRS) and host sediments, suggesting either that similar metabolisms operated in benthic and planktonic microbial communities or that benthic carbon fixation contributed organic matter to the host sediments. The isotopic fractionation between organic and inorganic carbon is as large as 44‰, implying the involvement of multiple levels of heterotrophic carbon processing, linked to phototrophy, secondary productivity, and methanotrophy. Whole-rock nitrogen isotope values in the range of −3.5 to + 1.9‰ are consistent with microbial community nitrogen fixation in a nitrate-limited ecosystem. These data suggest that nitrogen fixation, common in photosynthetic microbial mats in modern environments, operated in benthic settings in the coastal area of the mid-Paleoproterozoic Franceville sub-basin. The upwelling of deep, anoxic waters invoked for deposition of the upper part of the underlying FB1 Member suggests that basin-scale redox structure modulated nitrate availability in this otherwise oxic, shallow-marine basin shelf environment.

Considerations when using nutrient inventories to prioritize water quality improvement efforts across the US

Ongoing water quality degradation tied to nitrogen and phosphorus pollution results in significant economic damages by diminishing the recreational value of surface water and compromising fisheries. Progress in decreasing nitrogen and phosphorus pollution to surface water over the past two decades has been slow. Limited resources need to be leveraged efficiently and effectively to prioritize watersheds for restoration. Leveraging recent nitrogen and phosphorus inventories for the years 2002, 2007, and 2012, we extracted relevant flux and demand terms to help identify US subbasins that are likely contributing a disproportionate amount of point and non-point source nutrient pollution to surface water by exploring the mean spatial distribution of terrestrial anthropogenic surplus, agricultural surplus, agricultural nutrient use efficiency, and point source loads. A small proportion of the landscape, <25% of subbasin area of the United States, contains 50% of anthropogenic and agriculture nitrogen and phosphorus surplus while only 2% of landscape contributes >50% of point source loads into surface water. Point source loads are mainly concentrated in urban areas across the country with point source loading rates often exceeding >10.0 kg N ha−1 yr−1 and >1.0 kg P ha−1 yr−1. However, the ability for future upgrades to wastewater treatment plant infrastructure alone is unlikely to drive further improvement in water quality, outside of local water ways, since point source loads only account for ~4% of anthropogenic N and P surplus. As such, further progress in boosting nutrient use efficiency in agricultural production, usually lowest in areas of intensive livestock production, would likely contribute to the biggest gains to water quality restoration goals. This analysis and the corresponding database integrate multiple streams of information to highlight areas where N and P are being managed inefficiently to give decision makers a succinct platform to identify likely areas and sources of water quality degradation.

Morphometry of the Páez River hydrographic sub-basin, Cartago, Costa Rica

Morphometric studies provide information on the hydrological functioning in a basin. The objective of the present study was to determine morphometric parameters in the sub-basin of the PáezRiver, located in the province of Cartago, Costa Rica, necessary for land use planning within thebasin and its proper management. Morphometric construction was based on the 1:10,000 scale contour lines available for the Gran Area Metropolitana (translated as the Greater Metropolitan Area)and geographic information systems utilized to digitalize contour lines, drainages and watershed.Resulting from the morphometric analysis, a sub-basin area of 28.34 km2 and perimeter distanceof 47.4270 km were estimated. The sub-basin is comprised of 22 micro-basins and overall exhibitsa form factor value of 0.1171, thus indicating an elongated sub-basin. A compactness coefficientvalue of 2.4942 indicates an elongated basin. The sub-basin exhibits a concave hypsometric curve,where the peak of its altimetry distribution corresponds to altitudes between 3315 m and 980 m.The slope parameter has an average value of 29.3% slope. It is evident the role played by the PáezRiver sub-basin for the development of productive activities and water supply of some localities inthe province of Cartago.

The morphological response of the Tegnas alpine catchment (Northeast Italy) to a Large Infrequent Disturbance

A recent storm (27th–30th October 2018), named Vaia, hit most part of the Northeast of Italy affecting the geomorphic aspect of almost all mountain catchments of the area. The event triggered new instabilities such as windthrows, landslides and debris flows. At present, few studies dealt with the analysis of the impact of a Large Infrequent Disturbance at large catchment scale. This work provides a focus on the Tegnas Torrent Basin (Belluno Province) and aims at detecting how, where, and how much this storm affected the basin. Moreover, it integrates two different approaches considering both the dynamic and static aspects of the sediment, via DEM of Difference (DoD) and Index of Connectivity (IC), respectively. The Tegnas sub-basins responded contrastingly: the Bordina (volcanic origin and covered by pastures and spruce forests) was mainly affected by windthrows (7% of the sub-basin area) and landslides (0.5%), while the Angheraz (outcropping dolomite rocks), was stricken only by debris flows (1.0%). Morphological changes were clear along the entire channel network, with predominant erosion in the steepest upstream parts (over 2 m of the channel elevation), and deposition in the lower main valley floor (over 3 m of the channel elevation). The IC analysis along the instabilities highlighted that the windthrows occurred mainly in areas of high connectivity, which may be important for future management strategies. Moreover, the proposed integrated approach, based on the combination IC-DoD, permitted a detailed identification of sediment routing and a contemporary estimation of erosion and deposition volumes generated by a high magnitude low-frequency event. Based on these results, cascading processes are expected and further analysis are required to fully consider the impact of a Large Infrequent Disturbance.

РАСПРЕДЕЛЕНИЕ ГАЗОВ В ДОННЫХ ОТЛОЖЕНИЯХ ЮГО-ЗАПАДНОГО СУББАССЕЙНА ЮЖНО-КИТАЙСКОГО МОРЯ

For the first time, this paper presents the distribution of gases (CO2, hydrocarbon C1-C4, H2, He) in 39 gas samples in bottom sediments from 19 gravity cores located in the southwestern sub-basin of the South China Sea (known as Bien Dong). The surface sediments in the studied area are mostly silty clay. In general, the concentration of methane varies in a wide range of 0.5–440 ppm. Anomalous values of methane were detected at many locations along the slope area of the southwest sub-basin of the South China Sea. The value of 2.2 ppm could be considered as a background concentration of methane in the studied region. The presence of a large-scale degassing zone of methane in the studied area was proposed. Besides, heavy hydrocarbon gases (ethylene, ethane, propane, and butane) were also determined with the highest values up to 70 ppm, 124 ppm, and 50 ppm for ethylene, ethane and propane, respectively. In addition, data of carbon dioxide, hydro and helium suggest some anomalous values of H2 up to 56.7 ppm.

Mapping water inundation and inundated landuse which will formed due to development of Karian dam, Ci Berang Sub-Basin, Lebak Regency, Banten Province

Overpopulation and development in Java Island have caused changes in land use from productive into non-productive land. One of the changes occurring in Indonesia is the development of the Karian Dam as a Multi-Purpose Dam in the Ci Berang Sub-Basin. This study aims to determine the area of inundated water will covering land use and many villages caused by the construction of Karian Dam. The dam was started the construction in the year 2015 and will complete in the year 2019. The variables used in this study is the elevation of inundated water and the land use of the Ci Berang Sub-Basin. The data for inundated are water level at minimum, normal, and maximum, which combined with digital elevation model (DEM). The research used the landcover data generated from Landsat 8 OLI. The results explained that the Ci Berang Sub-Basin area would be affected by the inundated water is 1,479 Ha. The changes caused by the water inundation will affect the land use in the northern area of Ci Berang Basin those are shrubs, wetlands, plantations, and urban areas more than 54.57 Ha and vacant lots 16,14 Ha. The land use, which has the highest area of inundated water coverage was shrubs 53 % and wetlands 22 %. The inundated water caused many villages covered by water with the highest land use change was Tambak Village with 335.48 Ha, and the lowest was Sindangsari Village with 3.73 Ha.

Feasibility assessment of SHP potential using GIS-enhanced RS approach in poorly gauged river basin in Nigeria

• Combination of Remote Sensing, Geographic Information System and Natural Resources Conservation Service – Curve Number model is helpful in effective planning and management of watershed in the absence of information on hydrological, topographical and geological characteristics • Run of river (ROR) hydropower plants , utilizing instantaneous river flow were suggested for the identified sites in the study area. • 11 points out of the 58 points examine at 2 km interval were classified as a feasible potential site for hydropower development . In this paper, we present the result obtained by application of Remote Sensing (RS) data & Geographic Information System (GIS) procedure in the identification and selection of feasible sites for small hydropower (SHP) projects in Oyanmi River in the Benin-Owena drainage Basin in Nigeria, using Natural Resource Conservation Service-Curve Number (NRCS-CN) model. Catchment delineation, Sub-basin Area size, slope, Curve Number (CN), Land Use Land Cover (LULC), Digital Elevation Model (DEM), rainfall intensity, etc. were obtained by RS and Arc GIS tools. Data on rainfall were obtained from Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR) for the year 2018 and validated using Nigerian Meteorological Services Agency (NIMET) Lokoja synoptic station data and then utilized for the computation of simulated discharge. The simulated discharge were correlated with observed data obtained from a gauging station in the study area. The correlation between observed and simulated data yielded a good correlation result of 65% and 63% for rainfall and discharge respectively with good statistical significance P-value. Elevation values extracted from the DEM were used in calculating the available head utilized in evaluating the hydropower potentials across the 58 hydrometric mapped-out points. Based on the criteria that a viable SHP should have a minimum slope of 2% and 10 m available head, 11 points were identified in Oyanmi sub-basin with feasible power potential ranging from 393.849 kW to 16038.194 kW at 92% annual flow exceedance which if developed would improve access to energy and socio-economic development of the study area.