Hypsometric analysis and watershed management of Diyung watershed in north eastern India

The Diyung river descends in Nagaon district of Assam. After its confluence with main channel Kopili it causes enormous losses to life and property due to floods. Appropriate watershed treatment measures are, therefore, required for moderating the flood damage. In the present study landscape information viz., the hypsometric integral has been analysed. The Diyung watershed has been subdivided into 23 sub-watersheds for hypsometric analysis. The hypsometric integral for the entire Diyung watershed ranged from 0.14 to 0.56. According to the present study there are two stages of geologic/geomorphologic development, namely equilibrium stage and monadnock stage. The hypsometric integral indicates that surface runoff is the dominant process. Although static, the topographic characteristics indicate response of watershed to various natural phenomenon and dominant processes such as runoff and erosion. Based on the intensity of the processes sub-watershed can be prioritized for taking up appropriate conservation measures. The study also highlights the use of hypsometric integral for prioritizing watershed for planning engineering measures to mitigate the impact.     

GIS applications in morphometric analysis of Koshalya-Jhajhara watershed in northwestern India

The present paper deals with morphometric analysis of Koshalya-Jhajhara (K-J) watershed, tributaries of Ghaggar in northwestern India. The area forms a rugged topography having elevation range from 399 m to 1810 m MSL. Aster DEM and SOI toposheets have been used to calculate various parameters using Geographic Information System (GIS). Linear, areal and relief aspects for morphometric analysis were calculated using GIS. Total number of streams in the watershed are 991 out of which 543 are of 1^st order, 259 are of 2^nd order, 124 are of 3^rd order, 58 are of 4^th order and only 7 are of 5^th order. The order of stream determines the chances of flood in the stream. Higher the stream order more the probabilities of flood. The present paper indicates that K-J watershed is of 5^th order and less elongated in shape having lower peak flows of longer duration with dendritic pattern and having fine drainage texture. Bifurcation ratio varies from 3 to 5 which indicate that geological structures don’t have dominant influence on drainage pattern. High slope is witnessed in NE part and low slope in SW part with very low gradient ratio. Variables like stream frequency and drainage density determines the volume of the water discharge and its speed of flow in the river channels. Higher the stream frequency and drainage density more will be the probability of floods. These variables also effects temporal variations in the speed at which the water flows in the stream when flood reaches its peak.     

A numerical scheme for groundwater development in a watershed basin of basement terrain: a case study from India

The development of watershed basins to increase groundwater recharge potential is becoming a major issue in India due to an acute shortage of groundwater resources, resulting from the marked expansion of land-use activities and the explosive growth in population. It is necessary to study the regional characteristics in order to identify potential artificial groundwater recharge zones. A combination of morphometric analysis coupled with hydrogeological information is used to prepare a generalized scenario for watershed development plans. A numerical scheme is, thus, proposed for the relative evaluation of surface rock-permeability in relation to morphometry (stream order, stream length, drainage density, channel maintenance, overland flow, basin shape, etc.). An attempt is made, from the morphometrical studies of the Varaha watershed of the Precambrian Eastern Ghats basement terrain in Eastern India, to illustrate how the numerical scheme is helpful as a tool in watershed development planning programs. This method involves the designation of various recharge-related measures, based upon the relative ranking of surface-material permeability after comparison with the hydrogeological conditions of sub-basins of the river basin. The scheme can also help to pin-point areas of study on a local scale, and thus facilitate developmental programs to augment groundwater recharge.     

Spatio-temporal land cover changes in a semi-arid watershed: Central India

Land use/land cover change is a global phenomenon which reflects natural resources degradation and/or utilization. Remote sensing and GIS have been widely used to monitor such changes at watershed level. The present study evaluates the LU/LC change during 1989 - 2001 in a semi-arid watershed of central India. Geocoded satellite data of 1989 and 2001 on 1:50,000 scale, were visually interpreted to prepare thematic maps which were later digitized using ArcGIS softwares. The analysis shows that vast tracts of cultivated land have become uncultivated and at some places even converted to wasteland. However, the land under dense forest and open forest has decreased due to expansion of built-up land and other anthropogenic activities. Increase in area of uncultivated land, wasteland and decrease in cultivated land and open scrub is also supported by rainfall analysis, which shows a declining trend and a fall of 186.93 mm in average annual rainfall for 1986-2003 period. The change detection map prepared using land use/land cover of 1989 and 2001 as inputs shows that out of the total geographical area of the watershed, 25.78% of the watershed area has seen a change from one land use category to another, however rest 74.22% has remained unchanged.     

Optimal design of flood-control multi-reservoir system on a watershed scale

Flood events have the highest damage costs and losses among natural hazards. There are different types of measures to mitigate flood damage costs and their negative consequences. Application of flood-control reservoirs or detention dams, as one of the main measures, may decrease devastating flood effects or even may cause to intensify flood damages in the watershed by a poor design with tremendous construction costs. Optimal design of a flood-control multi-reservoir system can simultaneously minimize investment costs of constructions and potential flood damage costs. This study proposes a simulation-based optimization approach to optimize the design of multi-reservoirs for flood control in the watershed by coupling the MIKE-11 hydrodynamic model and the NSGA-II multi-objective optimization model. The present approach provides the Pareto optimal solutions between two conflict objectives of minimizing total investment costs and the expected flood damage costs in the watershed. Application of the proposed model for a small watershed in central part of Iran as a case study shows that optimal designs of multi-reservoir systems can efficiently reduce construction costs, flood peaks and their corresponding damage costs at the downstream reaches of the basin.     

Spectrum of climate change and streamflow alteration at a watershed scale

Worldwide, evidences of water cycle alteration and fresh water resources depletion are frequently reported with various magnitudes. This alteration in the hydrologic cycle is often regarded as a signal of the actual climate change. However, the debate on climate change seems to have preferentially focused on global-scale patterns such that the rich knowledge gathered in the domain is virtually less integrated to decision making at the watershed level. Indeed, the watershed apprehension of climate change is probably an imperative for sustainable water resources planning. The scope of the present study aligns with that imperative as it aims at conciliating patterns of climate change with observations of hydrologic alterations at the watershed level. Specifically, the paper describes the interplay between land-cover changes and the terrestrial water cycle disturbances under climate change at the global level. Thereafter, it reports a watershed-level analysis of streamflow, land-cover, PET and precipitation alteration. Specially, the case study focused on the Brazos River basin, located in the USA and shared by the states of Texas and New Mexico. From both regional and watershed prospects, signals of hydrologic alteration during the time period 1955–2014 are highlighted and then implications of climate change are discussed. The results show an overall longitudinal gradient of precipitation changes and a latitudinal gradient of PET changes across the Brazos watershed. However, these gradients of changes seem to be driven by regional climate components which extend beyond the physical boundary of the Brazos watershed. Mann–Kendall’s analysis of discharge time series (annual average, minimum and maximum) at 10 different stations exhibits meaningful contrasts from upstream to downstream. An assessment of land-cover changes shows critical patterns of landscape change across the watershed. The analyses depicted signals of urbanization sprawl and land-cover degradation. Specially, the significant statistical relationships observed between the time series of maximum green vegetation fraction (MGVF) and streamflow also indicate that the origin of the observed hydrologic alteration is anthropogenic. Ultimately, the results are discussed within the scope of climate change.     

流域水环境功能区划及其关键问题

针对现行水环境功能区划存在的6大问题,提出了以景观生态学、流域管理和水生态服务功能等为理论基础的,以水生态分区、水生态系统完整性评价、冲突分析等为区划途径的流域水环境功能区划。该区划方法及技术路线充分体现了国外趋势与国内管理要求:流域尺度、协调思想、因地制宜和动态性,并重点分析了概念内涵和技术操作程序。同时针对此区划的2大关键问题——协调人与自然、不同利益者冲突问题和确定分类管理功能区——提出了思路与解决途径。本研究有效地权衡了人类需求功能与水生态需求功能,协调了跨界冲突问题以及综合考虑了水资源利用、水环境改善和水生态保护的相互关系,为我国未来水环境管理和流域管理提供技术支持。     

Spatial prediction of soil properties in a watershed scale through maximum likelihood approach

Surface map of soil properties plays an important role in various applications in a watershed. Ordinary kriging (OK) and regression kriging (RK) are conventionally used to prepare these surface maps but generally need large number of regularly girded soil samples. In this context, REML-EBLUP (REsidual Maximum Likelihood estimation of semivariogram parameters followed by Empirical Best Linear Unbiased Prediction) shown capable but not fully tested in a watershed scale. In this study, REML-EBLUP approach was applied to prepare surface maps of several soil properties in a hilly watershed of Eastern India and the performance was compared with conventionally used spatial interpolation methods: OK and RK. Evaluation of these three spatial interpolation methods through root-mean-squared residuals (RMSR) and mean squared deviation ratio (MSDR) showed better performance of REML-EBLUP over the other methods. Reduction in sample size through random selection of sampling points from full dataset also resulted in better performance of REML-EBLUP over OK and RK approach. The detailed investigation on effect of sample number on performance of spatial interpolation methods concluded that a minimum sampling density of 4/km² may successfully be adopted for spatial prediction of soil properties in a watershed scale using the REML-EBLUP approach.     

Fluoride occurrence and mobilization in geo-environment of semi-arid Granite watershed in southern peninsular India

Plausible forms of fluoride (F) responsible for the persistence of fluoride toxicity in ground water of a granitic terrain of semi-arid region, which is the main source of drinking water, have been studied. The study area in Anantapur District of Andhra Pradesh, India, is one of the chronic regions with excess fluoride in groundwater and the region is under transformation into aridity due to poor rainfall and over-exploitation of groundwater. Geochemical analysis of soil, groundwater, and rock samples of the study area revealed the presence of other toxic elements also in addition to fluoride which need to be addressed in drinking water sector in near future. Soil fluoride leaching experiments demonstrated the probable mode of mobilization of F into the groundwater through natural recharge process during monsoon. Analysis of saturation indices indicates that the fluorite solubility alone is not attributable to the high fluoride content in groundwater. The groundwater flow controls fluoride mobilization in the study area as it is evidenced through fluoride concentration and electrical conductivity increase from catchment to downstream region. Creation of lesser fluoride groundwater sources through rainwater harvesting and artificial recharge of groundwater in catchment areas is suggested as a long-term sustainable safe drinking water strategy.     

Modeling the effects of controlled drainage at a watershed scale using SWATDRAIN

The recently developed SWATDRAIN model was employed to assess the impact of controlled drainage on the water table dynamics, subsurface drainage, and surface runoff in an agricultural watershed in Ontario, Canada. Controlled drainage was defined with a depth of 1.0 m to restrict flow at the drain outlet to maintain the water table at 0.5 m below the surface level during the winter (November–April) and at 0.6 m during the summer (June–August) months. The effects of the absence, or implementation, of drainage water management were predicted for the 3-year period of 1991–1993. Implementing controlled drainage resulted in a 16 % reduction in the mean annual drain flow, while increasing surface runoff by as much as 71 %. This indicates that overall watershed hydrology could be significantly impacted by the implementation of controlled drainage. This research demonstrates the SWATDRAIN model’s ability to predict the controlled drainage in small agricultural watersheds.     

Fractal analysis of major faults in India on a regional scale

The seismicity of a region is implicit of the causal faulting mechanisms and geodynamic diversity of the subsurface regime nucleating earthquakes of different magnitudes, several of which may be as devastating as ones historically reported in global perspective of tectonic complexity as in the case of India. Fractal analysis using box-counting method for the major fault networks across the country estimates fractal dimension, D_f, values to be varying between 0.88 and 1.36. The fault segments in parts of northwest Himalayas, northeast India and Indo-Gangetic plains, are observed to be associated with higher D_f values implicating high seismicity rates. On the other hand, low D_f values in the peninsular India indicate isolated pattern of the underlying faults. The fractal dimension is observed to be indicative of predominant faulting types — higher values conforming to thrust faulting mechanism while lower to strike slip tectonism.     

Fluoride dynamics in the granitic aquifer of the Wailapally watershed,Nalgonda District,India

High concentrations of fluoride (up to 7.6 mg/L) are a recognized feature of the Wailapally granitic aquifer of Nalgonda District, Andhra Pradesh, India. The basement rocks provide abundant sources of F in the form of amphibole, biotite, fluorite and apatite. The whole-rock concentrations of F in the aquifer are in the range 240–990 mg/kg. Calcretes from the shallow weathered horizons also contain comparably high concentrations of F (635–950 mg/kg). The concentrations of water-soluble F in the granitic rocks and the calcretes are usually low (1% of the total or less) but broadly correlate with the concentrations observed in groundwaters in the local vicinity. The water-soluble fraction of fluoride is relatively high in weathered calcretes compared to fresh calcretes.Groundwater major-ion composition shows a well-defined trend with flow downgradient in the Wailapally aquifer, from Na–Ca–HCO₃-dominated waters in the recharge area at the upper part of the catchment, through to Na–Mg–HCO₃ and ultimately to Na–HCO₃ and Na–HCO₃–Cl types in the discharge area in the lowest part. The evolution occurs over a reach spanning some 17 km. Groundwater chemistry evolves by silicate weathering reactions, although groundwaters rapidly reach equilibrium with carbonate minerals, favouring precipitation of calcite, and ultimately dolomite in the lower parts of the watershed. This precipitation is also aided by evapotranspiration. Decreasing Ca activity downgradient leads to a dominance of fluorite-undersaturated conditions and consequently to mobilisation of F. Despite the clear downgradient evolution of major-ion chemistry, concentrations of F remain relatively uniform in the fluorite-undersaturated groundwaters, most being in the range 3.0–7.6 mg/L. The rather narrow range is attributed to a mechanism of co-precipitation with and/or adsorption to calcrete in the lower sections of the aquifer. The model may find application in other high-F groundwaters from granitic aquifers of semi-arid regions.     

Morphometric analysis of a watershed of South India using SRTM data and GIS

An attempt has been made to study drainage morphometry and its influence on hydrology of Wailapalli watershed, South India. For detailed study we used Shuttle Radar Topographic Mission (SRTM) data for preparing Digital Elevation Model (DEM), aspect grid and slope maps, Geographical information system (GIS) was used in evaluation of linear, areal and relief aspects of morphometric parameters. The study reveals that the elongated shape of the basin is mainly due to the guiding effect of thrusting and faulting. The lower order streams are mostly dominating the basin. The development of stream segments in the basin area is more or less affected by rainfall. The mean Rb of the entire basin is 3.89 which indicate that the drainage pattern is not much influenced by geological structures. Relief ratio indicates that the discharge capability of these watersheds is very high and the groundwater potential is meager. These studies are very useful for planning rainwater harvesting and watershed management.     

Evaluating the influence of watershed characteristics on flood vulnerability of Markanda River basin in north-west India

Natural Hazards - Floods are recurrent events in the floodplains of Coochbehar district inundating and damaging considerable quantities of standing crops and hampering the livelihoods of thousands...     

An integrated flood inundation model for coastal urban watershed of Navi Mumbai,India

Most urban agglomerations located in the Mumbai coastal region in India are vulnerable to flooding due to increasing frequency of the short-duration heavy rainfall, by virtue of their location at foothills on one side and tidal variations on the other side. Steep slopes in the catchment ensure fast runoff and tidal variation adds to backwater effect in the drainage system, which together are favorable for flooding. The present study simulates the flood inundation due to heavy rainfall and high-tide conditions in a coastal urban catchment within Mumbai region with detention pond. Overland flow is modeled using a mass balance approach, which can adapt to hilly slopes and smoothly accommodate detention pond hydraulics. Dynamic wave channel routing based on finite element method captures the backwater effects due to tidal variation, and raster-based flood inundation model enables direct use of digital elevation model. The integrated model is capable of simulating detention pond hydraulics within the raster flood model for heavy rainfall events. The database required for the model is obtained from the geographical information system (GIS) and remote sensing techniques. Application of the integrated model to literature problems and the catchment of the study area for two non-flooding events gave satisfactory results. Further, the model is applied to an extreme rainfall event of July 26, 2005, coinciding with high-tide conditions, which revealed vulnerability of the area to flooding despite of an existing detention pond. A sensitivity analysis on the location of detention pond indicated that catchment response can be better governed by relocating the detention pond to upstream of existing detention pond especially when heavy rainfall events are becoming frequent.     

Variation of debris flow/flood formation conditions at the watershed scale in the Wenchuan Earthquake area

A channelized debris flow/flood generally originates from initial gully erosion by superficial runoff that evolves rapidly into massive erosion of the channel bed. Knowledge of the formation conditions of such events is crucial for accurate forecasting, and determination of rainfall and runoff thresholds for such hazards is a primary concern following a strong earthquake. This work proposed a framework for debris flow/flood formation at the watershed scale in two watersheds (area: 2.4 and 32.4 km²) in the Wenchuan Earthquake area (China). The critical runoff and rainfall conditions required for debris flow/flood formation were simulated and their annual variations investigated. Ultimately, the runoff conditions required for debris flow/flood formation in the two studied watersheds were calculated on an annual basis and found to increase in time. Similarly, following consideration of three different rainfall types, critical rainfall conditions were proposed that also showed an increasing tendency. The increase of rainfall and runoff conditions for debris flow/flood formation is attributable to both the recovery of vegetation and the reduction of source materials. In comparison with actual monitored flow behaviors and previously proposed rainfall thresholds, the results showed strong consistency and high forecasting efficiency.

     

Approaching water management at watershed scale using distributed water balances in the Yanuncay River basins (Ecuador)

In this study, the excess water generated during a 10-year period (1998–2008) in the upper and middle Yanuncay River basins is estimated. The distributed water balance method, which analyses the interaction between all the different parameters that form part of the water cycle in nature, was developed. To create the model, basic parameters such as rainfall, temperature, soil type and surface cover are required. Moreover, by using computer software such as Microsoft Office Excel and geographic information systems, it is possible to obtain monthly data showing the water excess and generate thematic maps which allow for an effective monitoring of the behaviour of the middle and upper Yanuncay River basins. This study takes the spatial variability of the various factors that influence the behaviour of a basin into account. This allows determining zones with greater water excess, which are areas that would need to be protected. The model can easily incorporate new data such as land use and surface cover (based on time frames) which would facilitate the comparison of different scenarios.