Extenuating the parameters using HEC-HMS hydrological model for ungauged catchment in the central Omo-Gibe Basin of Ethiopia

Characteristics of ungauged catchments can be studied from the hydrological model parameters of gauged catchments. In this research, discharge prediction was carried out in ungauged catchments using HEC-HMS in the central Omo-Gibe basin. Linear regression, spatial proximity, area ratio, and sub-basin mean were amalgamated for regionalization. The regional model parameters of the gauged catchment and physical characteristics of ungauged catchments were collated together to develop the equations to predict discharge from ungauged catchments. From the sensitivity analysis, crop coefficient (CC), storage coefficient (R), constant rate (CR), and time of concentration (TC) are found to be more sensitive than others. The model efficiency was evaluated using Nash–Sutcliffe Efficiency (N_SE) which was greater than 0.75, varying between ?10% and +10% and the coefficient of determination (R²) was approximated to be 0.8 during the calibration and validation period. The model parameters in ungauged catchments were determined using the regional model (linear regression), sub-basin mean, area ratio, and spatial proximity methods, and the discharge was simulated using the HEC-HMS model. Linear regression was used in the prediction where p-value ≤ 0.1, determination coefficient (R²) = 0.91 for crop coefficient (CC) and 0.99 for maximum deficit (MD). Constant rate (CR), maximum storage (MS), initial storage (IS), storage coefficient (R), and time of concentration (TC) were obtained. The result is that an average of 30 m³/s and 15 m³/s as the maximum monthly simulated flow for ungauged sub-catchments, i.e. Denchiya and Mansa of the main river basin .     

Impact of river network type on the time of concentration

Time of concentration (T _c) is one of the frequently used parameters to characterize the response of a drainage basin to a rainfall event. Conceptually, it is the time runoff travels from the hydraulically most distant location in a basin to its outlet. T _c was found to vary depending on river basin characteristics such as slope, soil infiltration, and flow path. In this study, we investigate if the drainage network type information can be used as an input to hydrological models, by estimating the time of concentration separately for different network types. Sixty-eight basins which have areas ranging from 24 to 965 km² in arid and non-arid regions of the USA are compared and the effect of climate is also analyzed. It is found that the slope of the linear relationship between T _c and the maximum hydraulic length of flow path shows different correlation coefficients ranging from 0.80 to 0.98 for different network types. It is observed that the slope of the regression line between T _c and the maximum hydraulic length of flow path is the lowest for dendritic networks (slope of 0.26), while pinnate networks have the steepest slope of the regression line (slope of 0.59). This indicates that the drainage network type has a direct impact on the hydrological behavior of the basin and can represent a direct input in hydrological modeling.     

Spatial scale dependence of sediment dynamics in a gullied rolling loess region on the Loess Plateau in China

Sediment dynamics is still imperfectly understood, especially at spatial scale in the highly erodible region of the Loess Plateau, and few studies have been heretofore conducted. Using 5-year continuous water and sediment records, three plots and three basins in the gullied rolling loess region were selected and sediment dynamics at spatial scale was studied. Results showed that the floods, where the peak discharge (Q _p) did not come earlier than the sediment peak, were predominant in slope zones, occupying >90 and >70% of the total for the Mao slope and for the Entire slope, respectively. However, in basins, most of the sediment peaks (C _p) lagged behind Q _p, implying that slope zone was the main origin of sediment. More than 50% of the events presented clockwise hysteresis loops in the Mao slope area, while almost all the events had anticlockwise hysteresis loops in basins. This can be attributed to less occurring frequency of hyperconcentrated flow, as well as its instability in slope zones, compared to those in the basins. Within these contexts, gravitational erosion made the highest sediment concentration (C) in Tuanshangou basin and median developing status of C-discharge (C–Q) relationships in the Entire slope area. This study provides insights into the protection of slope surface and disruption of the development of hyperconcentrated flow to reduce soil loss.     

Landscape variations in stream water SO4 and δSSO4 in a boreal stream network

Despite reduced anthropogenic deposition during the last decades, deposition sulphate may still play an important role in the biogeochemical cycles of S and many catchments may act as net sources of S that may remain for several decades. The aim of this study is to elucidate the temporal and spatial dynamics of both SO₄²⁻ and δ³⁴S_SO4 in stream water from catchments with varying percentage of wetland and forest coverage and to determine their relative importance for catchment losses of S. Stream water samples were collected from 15 subcatchments ranging in size from 3 to 6780 ha, in a boreal stream network, northern Sweden. In forested catchments (<2% wetland cover) S-SO₄²⁻ concentrations in stream water averaged 1.7 mg L⁻¹ whereas in wetland dominated catchments (>30% wetland cover) the concentrations averaged 0.3 mg L⁻¹. A significant negative relationship was observed between S-SO₄²⁻ and percentage wetland coverage (r² = 0.77, p < 0.001) and the annual export of stream water SO₄²⁻ and wetland coverage (r² = 0.76, p < 0.001). The percentage forest coverage was on the other hand positively related to stream water SO₄²⁻ concentrations and the annual export of stream water SO₄²⁻ (r² = 0.77 and r² = 0.79, respectively). The annual average δ³⁴S_SO4 value in wetland dominated streams was +7.6‰ and in streams of forested catchments +6.7‰. At spring flood the δ³⁴S_SO4 values decreased in all streams by 1‰ to 5‰. The δ³⁴S_SO4 values in all streams were higher than the δ³⁴S_SO4 value of +4.7‰ in precipitation (snow). The export of S ranged from 0.5 kg S ha⁻¹ yr⁻¹ (wetland headwater stream) to 3.8 kg S ha⁻¹ yr⁻¹ (forested headwater stream). With an average S deposition in open field of 1.3 kg S ha⁻¹ yr⁻¹ (2002-2006) the mass balance results in a net export of S from all catchments, except in catchments with >30% wetland. The high temporal and spatial resolution of this study demonstrates that the reducing environments of wetlands play a key role for the biogeochemistry of S in boreal landscapes and are net sinks of S. Forested areas, on the other hand were net sources of S.     

Morphometric analysis of Suketi river basin,Himachal Himalaya,India

Suketi river basin is located in the Mandi district of Himachal Pradesh, India. It encompasses a central inter-montane valley and surrounding mountainous terrain in the Lower Himachal Himalaya. Morphometric analysis of the Suketi river basin was carried out to study its drainage characteristics and overall groundwater resource potential. The entire Suketi river basin has been divided into five sub-basins based on the catchment areas of Suketi trunk stream and its major tributaries. Quantitative assessment of each sub-basin was carried out for its linear, areal, and relief aspects. The analysis reveals that the drainage network of the entire Suketi river basin constitutes a 7th order basin. Out of five sub-basins, Kansa khad sub-basin (KKSB), Gangli khad sub-basin (GKSB) and Ratti khad sub-basin (RKSB) are 5th order sub-basins. The Dadour khad sub-basin (DKSB) is 6th order sub-basin, while Suketi trunk stream sub-basin (STSSB) is a 7th order sub-basin. The entire drainage basin area reflects late youth to early mature stage of development of the fluvial geomorphic cycle, which is dominated by rain and snow fed lower order streams. It has low stream frequency (Fs) and moderate drainage density (Dd) of 2.69 km/km ². Bifurcation ratios (Rb) of various stream orders indicate that streams up to 3rd order are surging through highly dissected mountainous terrain, which facilitates high overland flow and less recharge into the sub-surface resulting in low groundwater potential in the zones of 1st, 2nd, and 3rd order streams of the Suketi river basin. The circulatory ratio (Rc) of 0.65 and elongation ratio (Re) of 0.80 show elongated nature of the Suketi river basin, while infiltration number (If) of 10.66 indicates dominance of relief features and low groundwater potential in the high altitude mountainous terrain. The asymmetry factor (Af) of Suketi river basin indicates that the palaeo-tectonic tilting, at drainage basin scale, was towards the downstream right side of the drainage basin. The slope map of Suketi river basin has been classified into three main zones, which delineate the runoff zone in the mountains, recharge zone in the transition zone between mountains and valley plane, and discharge zone in the plane areas of Balh valley.     

Hydrogeochemistry of Fe and Mn in small boreal streams: The role of seasonality, landscape type and scale

Stream water from a stream network of 15 small boreal catchments (0.03-67 km²) in northern Sweden was analyzed for unfiltered (total) and filtered (<0.4 μm) concentrations of iron (Fe_tot and Fe_<0.4) and manganese (Mn_tot and Mn_<0.4). The purpose was to investigate the temporal and spatial dynamics of Fe, Mn and dissolved organic carbon (DOC) as influenced by snow melt driven spring floods and landscape properties, in particular the proportion of wetland area. During spring flood, concentrations of Fe_tot, Fe_<0.4, Mn_tot, Mn_<0.4 and DOC increased in streams with forested catchments (<2% wetland area). In catchments with high coverage of wetlands (>30% wetland area) the opposite behavior was observed. The hydrogeochemistry of Fe was highly dependent on wetlands as shown by the strong positive correlation of the Fe_tot/Al_tot ratio with wetland coverage (r² = 0.89, p < 0.001). Furthermore, PCA analysis showed that at base flow Fe_tot and Fe_<0.4 were positively associated with wetlands and DOC, whereas they were not associated during peak flow at spring flood. The temporal variation of Fe was likely related to varying hydrological pathways. At peak discharge Fe_tot was associated with variables like silt coverage, which highlights the importance of particulates during high discharge events. For Mn there was no significant correlation with wetlands, instead, PCA analysis showed that during spring flood Mn was apparently more dependent on the supply of minerogenic particulates from silt deposits on the stream banks of some of the streams. The influence of minerogenic particulates on the concentration of, in particular, Mn was greatest in the larger, lower gradient streams, characterized by silt deposits in the near-stream zone. In the small forested streams underlain by till, DOC was of greater importance for the observed concentrations, as indicated by the positive correlation of both Fe_tot and Fe_<0.4 with DOC (r² = 0.77 and r² = 0.76, p < 0.001) at the smallest headwater forest site. In conclusion, wetland area and DOC were important for Fe concentrations in this boreal stream network, whereas silt deposits strongly influenced Mn concentrations. This study highlights the importance of studying stream water chemistry from a landscape perspective in order to address future environmental issues concerning mobility of Fe, Mn and associated trace metals.     

Effect of using multiple stream gauging stations on calibration of hydrologic parameters and estimation of hydrograph of ungauged neighboring basin

In this study, Hydrologic Engineering Center-Hydrologic Modeling System is used to simulate hydrologic processes in a watershed in Western Black Sea Region that frequently experiences flooding. The region is mountainous with steep hill slopes and receives high precipitation throughout the year. There are three stream gauging stations in the basin whose data are available for calibration and validation of hydrologic parameters. Simulations are performed for different scenarios to investigate the effect of using multiple stream gauging stations’ data on catchment wide calibration and validation of hydrologic parameters. Furthermore, performance of using calibrated internal stream gauging stations’ flow data in the estimation of hydrologic parameters in an assumed neighboring ungauged basin was assessed. It is found that using data of multiple stream gauging stations for calibration and validation gives satisfactory results for direct runoff hydrograph but the peak discharge predictions are not improved. The study results suggest that using data of internal stream gauging stations enables improved understanding of internal dynamics and transport in the basin and better predicted direct runoff hydrograph for the assumed neighboring ungauged basin.     

Effect of watershed partitioning on hydrologic parameters and estimation of hydrograph of an ungauged basin: a case study in Gokirmak and Kocanaz,Turkey

The main goal of this study is to investigate the effect of the size of the subbasins of a watershed on the hydrologic parameters and their spatial variability in an estimation of the hydrologic parameters and hydrograph of a neighbouring ungauged basin. In this paper, Hydrologic Engineering Center-Hydrologic Modelling System (HEC-HMS), a semi-distributed hydrologic model, is used to calibrate and cross-validate two flood events occurred in 1998 and then validate four other flood events occurred in 1991, 1994, 2002, and 2009 in Gokirmak Basin in Western Black Sea Region, Turkey. The basin is divided into seven different subbasins to investigate the effect of watershed partitioning on calibrated hydrologic parameters of each subbasin using the peak-weighted root mean square error method as an objective function and the hydrograph at the outlet of the whole basin. It is found out that as the geometric magnitudes of the subbasins changed, the calibrated values of the hydrologic parameters of those subbasins changed as well. Then, a neighbouring basin, Kocanaz, is considered as an assumed neighbouring ungauged basin to investigate the effect of watershed partitioning of a gauged basin on the estimation of hydrograph of a neighbouring ungauged basin. Hydrologic parameters and direct runoff hydrograph of assumed ungauged neighbouring basin are estimated from the hydrologic parameters of the HEC-HMS calibration results of Gokirmak. Statistical indicators of the simulation results for each basin partitioning were graded with respect to the boundary values of the simulation outputs to find the best alternative. The grading results show that the simulation results with a single basin gave better representation among all other partitioning except two flood events.     

A Unified Assessment of Hydrologic and Biogeochemical Responses in Research Watersheds in Eastern Puerto Rico Using Runoff–Concentration Relations

An examination of the relation between runoff rate, R, and concentration, C, of twelve major constituents in four small watersheds in eastern Puerto Rico demonstrates a consistent pattern of responses. For solutes that are not substantially bioactive (alkalinity, silica, calcium, magnesium, sodium, and chloride), the log(R)–log(C) relation is almost linear and can be described as a weighted average of two sources, bedrock weathering and atmospheric deposition. The slope of the relation for each solute depends on the respective source contributions to the total river load. If a solute were strictly derived from bedrock weathering, the slope would be ?0.3 to ?0.4, whereas if strictly derived from atmospheric deposition, the slope would be approximately ?0.1. The bioactive constituents (dissolved organic carbon, nitrate, sulfate, and potassium), which are recycled by plants and concentrated in shallow soil, demonstrate nearly flat or downward-arched log(R)–log(C) relations. The peak of the arch represents a transition from dominantly soil-matrix flow to near-surface macropore flow, and finally to overland flow. At highest observed R (80 to >90 mm/h), essentially all reactive surfaces have become wetted, and the input rate of C becomes independent of R (log(R)–log(C) slope of –1). The highest R are tenfold greater than any previous study. Slight clockwise hysteresis for many solutes in the rivers with riparian zones or substantial hyporheic flows indicates that these settings may act as mixing end-members. Particulate constituents (suspended sediment and particulate organic carbon) show slight clockwise hysteresis, indicating mobilization of stored sediment during rising stage.     

降雨和地形地貌对水文模型模拟结果的影响分析

概念性水文模型数量众多,判断模型是否适合研究流域可以通过模拟结果来体现,但是熟悉流域的产汇流特性可以筛选模型,从根源上大量减少工作量,也可以解决相似流域无资料的问题。选取6种概念性水文模型,以马渡王、板桥和志丹这3个半湿润与半干旱流域为研究区域,探讨流域特性与模型结构之间的关系,并通过降雨和地形地貌分析其对模型模拟结果的影响。研究结果表明,流域地形及植被对产汇流过程有重要影响,由于局部产流现象严重,河道坡度影响大于流域平均坡度,当区域气候条件相差不大时,地形地貌比降雨对流域产汇流特性影响更大。因此对于水文模型的选择,可以在熟悉流域产汇流特性的基础上因地制宜,必要时可以增加适合研究流域的模块来获得更好的预报,在半干旱与半湿润流域,同时具有蓄满和超渗机制的模型能得到更好的应用。     

流域地貌结构因子对径流特征的影响分析

选取淮河两个主要暴雨中心的11个中小流域为研究对象,分析流域地貌结构因子(流域高程曲线特征值等)对其水文响应特征(多年平均径流系数、流量历时曲线斜率值)的影响.研究发现,流域高程曲线积分值及其斜率对径流特征影响最大.多年平均径流系数、流量历时曲线高流量阶段的斜率值(S_fh)与高程曲线斜率成正比,确定性系数达到0.77和0.67;而流量历时曲线低流量阶段的斜率值(S_fl)与高程曲线积分值也成正相关,确定性系数达0.65.这表明:在地形起伏较大的流域,其蓄水能力较弱,容易造成暴雨洪水过程的陡涨陡落,且多年平均降雨径流系数较大;反之在较为平坦的流域,其径流响应相对缓慢,表现出较强的流域调蓄能力.     

Induced channel enlargement in small urban catchments,Armidale, New South Wales

Surveys of stream channels in 14 small catchments within and adjacent to Armidale, northern New South Wales, revealed that urban affected streams were four times larger (on average) than adjacent rural streams. The enlargement of such channels is frequently attributed to increased urban storm runoff. In this case, however, there is no apparent linkage between the degree of urban development and the magnitude of channel enlargement. Rather, it appears that gullying is initiated by more direct disturbances to these channel boundaries, such as realignment and the building of road crossings. Once gullying has been initiated the degree of channel enlargement seems to be a function of slope; the enlargement of channels in the steeper headwater urban catchments being significantly greater than that in the lower reaches. For incipiently unstable channels such as these, the more conventional erosion control measures may be inadequate.     

The slope aspect: A predisposing factor for landsliding?

The influence of slope aspect on the distribution of landslides was studied in the Milia and Roglio basins in Tuscany, Italy. For each basin, the new Tuscany region landslide inventory that was initiated in 2010 was used. The landslides were split into separate datasets based on their prevailing movement typology. To assess the results that were obtained from the different slope aspect values, maps of the lithology, slope angle, distances to streams, and distances to tectonic lineaments were included in the bivariate statistical analysis as comparison terms. For each basin, all of the geo-environmental factor maps were compared with the different landslide typologies with GIS software. Pearson's Chi² (χ²) coefficient was used to test the degree of spatial association between each predictor variable and landslide type. In addition, Cramer's V test was used to quantify the strength of the degree of association. Next, a conditional analysis was applied to all of the possible combinations that occurred between the slope aspect and other landslide-predisposing factors. Overall, the slope aspect significantly affected the distribution of superficial landslide types, but apparently not that of other landslide types.     

分项调查与水文模型相结合的九龙江流域天然径流量计算

由于人类活动影响,水文站的实测径流过程普遍发生显著变化,而大量水资源分析计算工作必须以天然径流量为基础.以九龙江流域为例,提出将分项调查法与水文模型法相结合的流域天然径流量综合还原法,即采用分项调查法对主要水文站控制集水区的实测径流数据做还原计算,利用还原后的径流数据构建以子流域为单元的SWAT降雨径流模型,进而通过参...     

Reconstruction and post-event analysis of a flash flood in a small ungauged basin: a case study in Slovak territory

Flash floods are one of the major natural hazards occurring in small streams with a negative effect on the country as well as on human lives. Heavy rainfall occurred on July 20, 2014 and July 21, 2014 and caused severe surface water flooding and a flash flood in the Malá Fatra National Park (Slovakia). The most affected was Vrátna Valley with the Varínka stream. This study presents a reconstruction and post-event analysis of a flash flood on small ungauged basin located in this protected area of Slovakia. The reconstruction included hydraulic terrain measurements on estimating the flood’s culmination and documenting the flood’s development. The measurements were taken at three cross sections of the Varínka stream. This paper is focused mainly on post-event analysis of the Varínka stream in two profiles: Strá?a (gauged profile) and Tiesňavy (ungauged cross section). Subsequently, the extremeness of the flash flood was preliminary evaluated. Results of the post-event analysis showed that the July 2014 flood was not the highest flood in this area despite its catastrophic consequences. By studying historical materials, we came to the conclusion that in the past (e.g. in 1848 or 1939) some devastating floods in this area had occurred, which had disastrous consequences for the population. The second part of the study is focused on comparing this flash flood with three major floods which have occurred in Slovak territory since 1998. The first flood occurred on the 20th of July, 1998 on the Malá Svinka stream, and the two others are floods which occurred on the 7th of June, 2011 in the Small Carpathian Mountains: on the Gidra stream in Píla village and on the Parná stream in Horné Ore?any village. Such comparison of flash floods from different geographical regions and different rainfall events can provide comprehensive information about their regimes, threats and disastrous effects.     

Drainage morphometry and its influence on hydrology in an semi arid region: using SRTM data and GIS

An attempt has been made to study drainage morphometry and its influence on hydrology of Peddavanka watershed, South India. Drainage networks for the sub-basins were derived from topographical map (1:50,000) and Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM) data used for preparing elevation, slope and aspects maps. Geographical information system (GIS) was used in evaluation of linear, areal and relief aspects of morphometric parameters. The study reveals that SRTM DEM and GIS-based approach in evaluation of drainage morphometric parameters and their influence on hydrological characteristics at watershed level is more appropriate than the conventional methods. The mean Bifurcation ratio (R _b) of the entire basin is 3.88 which indicate that the drainage pattern is not much influenced by geological structures. VIII sub-basin have high elongation ratio (R _e), basin relief (B _h), Ruggedness number (Rn) and time of concentration (T _c). It indicates that the erosion and peak discharges are high in these basins. Therefore, the construction of the check dams and earth dams will help in reducing peak discharge on the main channel. These studies are very useful for implementing rainwater harvesting and watershed management.     

Stream analysis of small drainage basins in an ancient landform,Korean Peninsula

Much of the topography of Korea is ancient, but many Quaternary fault outcrops and marine terraces have been observed in the southeastern part of the Korean Peninsula. Sufficient evidence of a Quaternary fault is lacking in the geological features of the commercially developed Jukbyun and Uljin areas. Knickpoints that develop on streams can be formed by tectonic activity such as faulting and folding, or can result simply from the differential erosion rates of bedrock. In this study, we investigated the relationship between stream steepness and faults in the Jukbyun area. Stream profile analyses of the Bugu and Namdae basins were performed using a digital elevation model to estimate Quaternary tectonic movements. Stream parameters obtained from analysis of the longitudinal stream profiles of the Bugu and Namdae drainage basins in the northeastern part of the Korean Peninsula indicated neotectonic movement. Thirty of the thirty-nine knickpoints that developed in the downstream areas of the fluvial channels corresponded to fault zones. It is thought that fault activity results in knickpoints in river systems. The normalized relative slope (K_sn) value (54.9) of the BS1 stream in the Bugu drainage basin was higher than that (28.8–36.3) of the other streams in both basins, despite a similar lithology to NS1 and NS2. Therefore, we concluded that stream steepness might be a result of tectonic forcing rather than a product of rock strength in the study area and that stream parameters could provide indirect evidence of Quaternary tectonics in ancient landforms.     

1961-2010年西藏雅鲁藏布江流域降水量变化特征及其对径流的影响分析

采用1961-2010年雅鲁藏布江流域6个气象站近50 a降水量的实测数据,统计降水量的年、干季、湿季平均序列;结合流域6个水文站近50 a年径流序列资料,分析雅鲁藏布江流域降水变化特征及其对径流量的影响. 研究表明： 雅鲁藏布江流域1961-2010年近50 a年平均降水量表现为不显著增加,增加速率为3.3 mm·（10a）^-1,其中干季、湿季分别为1.9 mm·（10a）^-1 和1.4 mm·（10a）^-1,均为增加趋势;降水量的年代际变化在20世纪60年代相对偏多,70年代较平稳,而80年代为最少,到90年代有所回升,21世纪前10 a降水量处于不显著的增多态势. 雅鲁藏布江径流的变差系数C_V值在0.15~0.40之间,年际变化较小. 径流的年代际变化总体上存在一定的周期性波动,20世纪60年代是一个相对的丰水期,70年代减少,80年代达到最小值,之后径流有所回升,进入21世纪前10 a呈不显著增加趋势. 年、湿季尺度上径流量和降水量的相关显著,湿季作为径流主要形成期,其降水量的多寡直接影响流域径流量的丰枯,湿季降水量的增减影响着流域径流量的增减. 由此可见,降水变化是雅鲁藏布江天然径流最主要影响因子,最终也决定了雅鲁藏布江流域年径流量的丰枯.     

Tracing stream leakage towards an alluvial aquifer in a mountain basin using environmental isotopes

Stream–aquifer relationships in mountain basins are of great relevance because they control the water balance and, with it, the amount of resources (whether surface water or ground water) available for ecological and human demands. In this paper, this relationship is studied using environmental isotopes (δ¹⁸O and δD) to identify the occurrence of stream recharge in the Arbúcies River basin (NE Spain). Isotopic data from 51 natural springs define the local altitudinal gradient. This function is weighted by the proportional area above each point, given by the hypsometric curve, in order to estimate the isotopic stream water content as the contribution of runoff from incremental elevations. Stream water isotopes from two surveys are compared with hypsometrically averaged isotopic values to check for the appropriateness of this approach. Results show that it is more suitable when subsurface flows from surface formations, such as alluvial deposits, are the main contributors to stream discharge than when it derives from a single rainfall event. The characterization of stream isotope values is used as a key factor in identifying stream leakage to an unconfined alluvial aquifer in the lower reach of the Arbúcies River.     

Organic geochemistry of the Vindhyan sediments: Implications for hydrocarbons

The organic geochemical methods of hydrocarbon prospecting involve the characterization of sedimentary organic matter in terms of its abundance, source and thermal maturity, which are essential prerequisites for a hydrocarbon source rock. In the present study, evaluation of organic matter in the outcrop shale samples from the Semri and Kaimur Groups of Vindhyan basin was carried out using Rock Eval pyrolysis. Also, the adsorbed low molecular weight hydrocarbons, methane, ethane, propane and butane, were investigated in the near surface soils to infer the generation of hydrocarbons in the Vindhyan basin. The Total Organic Carbon (TOC) content in shales ranges between 0.04% and 1.43%. The S₁ (thermally liberated free hydrocarbons) values range between 0.01–0.09 mgHC/gRock (milligram hydrocarbon per gram of rock sample), whereas the S₂ (hydrocarbons from cracking of kerogen) show the values between 0.01 and 0.14 mgHC/gRock. Based on the T_max (temperature at highest yield of S₂) and the hydrogen index (HI) correlations, the organic matter is characterized by Type III kerogen. The adsorbed soil gas, CH₄ (C₁), C₂H₆ (C₂), C₃H₈ (C₃) and nC₄H₁₀, (nC4), concentrations measured in the soil samples from the eastern part of Vindhyan basin (Son Valley) vary from 0 to 186 ppb, 0 to 4 ppb, 0 to 5 ppb, and 0 to 1 ppb, respectively. The stable carbon isotope values for the desorbed methane (δ¹³C₁) and ethane (δ¹³C₂) range between −45.7‰ to −25.2‰ and −35.3‰ to −20.19‰ (VPDB), respectively suggesting a thermogenic source for these hydrocarbons. High concentrations of thermogenic hydrocarbons are characteristic of areas around Sagar, Narsinghpur, Katni and Satna in the Son Valley. The light hydrocarbon concentrations (C₁–C₄) in near surface soils of the western Vindhyan basin around Chambal Valley have been reported to vary between 1–2547 ppb, 1–558 ppb, 1–181 ppb, 1–37 ppb and 1–32 ppb, respectively with high concentrations around Baran-Jhalawar-Bhanpur-Garot regions (Kumar et al., 2006). The light gaseous hydrocarbon anomalies are coincident with the wrench faults (Kota – Dholpur, Ratlam – Shivpuri, Kannod – Damoh, Son Banspur – Rewa wrench) in the Vindhyan basin, which may provide conducive pathways for the migration of the hydrocarbons towards the near surface soils.