Sabarmati River Basin Research Articles

Limitation of automatic watershed delineation tools in coastal region

ABSTRACTIn this research article, the Sabarmati river basin, India, which joins the Gulf of Khambhat, has been chosen to demonstrate the limitation of various automatic watershed delineation tools. The basin area of the river has been delineated using CARTOSAT 1 (20 m), ASTER V2 (30 m) and SRTM (90 m) Digital Elevation Models (DEMs) with ArcGIS Hydrology, ArcHydro and ArcSWAT automatic watershed delineation tools. Delineation of Sabarmati river using ASTER V2 (30) DEM by ArcSWAT automatic watershed delineation tool produced the best results with an error of only 0.75%, as compared to the area reported in India WRIS. The SRTM DEM performed consistently better than other two DEMs in case of all three automatic watershed delineation tools and produced only 2.99% average error. ArcSWAT automatic watershed delineator is the most accurate watershed delineation tool in comparison to other two tools and produced a lowest average error of 1.57%. ArcGIS Hydrology tool, using all the DEMs, produced an average error of 11.55%, which is the highest amongst all of the three tools. In general, the automatic delineated stream network fails to join the main river and some area of the watershed is always left out.

Rapid seismic hazard assessment of the Sabarmati River basin in Gujarat State, Western India using GIS techniques

The Sabarmati River basin, Gujarat State, western India is one of the major river basins of Gujarat State, playing host to major cities such as Ahmedabad and Gandhinagar, both of which are important economic and political capitals of Gujarat State. In the study reported here, we collected available information on the Sabarmati River basin, Gujarat State in terms of geology, tectonics, seismicity, and shear-wave velocity and assimilated and integrated this information into a geographical information system (GIS) platform to generate a rapid first-order seismic hazard map of the area. The integration of different criteria, such as peak ground acceleration, amplification factor, geology and geomorphology, liquefaction, and seismotectonics critical to seismic hazard, was performed following pair-wise comparison using the analytical hierarchy process, wherein each thematic map was assigned a weight on a 1 to 5 scale depending on its contribution to the seismic hazard. Seismic hazard was evaluated using a numerical rating scheme with the help of the GIS. Analysis of the generated map revealed that the seismic hazard is highest in the southeastern part of the area, moderate in the central part, and lowest in the northeastern part comprising the Aravalli Range. The seismic hazard map also shows that almost 40% of the study area, namely that comprising basins of the Sabarmati River and its tributaries, is prone to high seismic hazard. Our results show that it is possible to generate a macro-level seismic hazard map by integrating available information and that this map is a useful tool for urban planners and helps in zeroing in on the areas where seismic microzonation or site-specific studies are required.

Paleoenvironmental implications and drainage adjustment in the middle reaches of the Sabarmati river, Gujarat: Implications towards hydrological variability

The dryland fluvial sequences exposed in the lower part of the Gujarat alluvial plain are investigated for palaeohydrological/palaeoclimatic reconstruction using conventional sedimentology, grain size analyses supported by optical chronology. Considering that the study area is cradling large-scale constructional activities, an attempt has also been made to assess the geotechnical properties of the sediments.It has been observed that the lower reaches of the Sabarmati valley have preserved record of fluvial aggradation since MIS-5 (90 ka) to MIS-3 (47 ka) whereas the onset of aeolian processes began at around 12 ka. Based on the sediment texture, the alluvial sequences are divided into the lower and upper units. The lower fluvial sequence is dated to 90–63 ka whereas the upper fluvial sequence is dated to 47 ka. The stratigraphic marker red soil is dated to 63 ka. The study indicates that the terrain experienced tectonic perturbations after ∼12 ka which was responsible for the shifting of the Sabarmati river from regional NE-SW to N-S which is more pronounced towards the upstream of the Sabarmati river basin while the landscape stability is observed towards the downstream consisting of the older alluvium dated to 90 ka. Geotechnical investigation reveals potentially liquefiable sand, which however have been compacted due to large scale calcretisation since their deposition.

Modeling of Rainfall-Runoff Correlations Using Artificial Neural Network-A Case Study of Dharoi Watershed of a Sabarmati River Basin, India

The use of an Artificial Neural Network (ANN) is becoming common due to its ability to analyse complex nonlinear events. An ANN has a flexible, convenient and easy mathematical structure to identify the nonlinear relationships between input and output data sets. This capability could efficiently be employed for the different hydrological models such as rainfall-runoff models, which are inherently nonlinear in nature. Artificial Neural Networks (ANN) can be used in cases where the available data is limited. The present work involves the development of an ANN model using Feed-Forward Back Propagation algorithm for establishing monthly and annual rainfall runoff correlations. The hydrologic variables used were monthly and annual rainfall and runoff for monthly and annual time period of monsoon season. The ANN model developed in this study is applied to Dharoi reservoir watersheds of Sabarmati river basin of India. The hydrologic data were available for twenty-nine years at Dharoi station at Dharoi dam project. The model results yielding into the least error is recommended for simulating the rainfall-runoff characteristics of the watersheds. The obtained results can help the water resource managers to operate the reservoir properly in the case of extreme events such as flooding and drought.

Evaluation of water quality index for River Sabarmati, Gujarat, India

An attempt has been made to develop water quality index (WQI), using six water quality parameters pH, dissolved oxygen, biochemical oxygen demand, electrical conductivity, nitrate nitrogen and total coliform measured at three different stations along the Sabarmati river basin from the year 2005 to 2008. Rating scale is developed based on the tolerance limits of inland waters and health point of view. Weighted arithmetic water quality index method was used to find WQI along the stretch of the river basin. It was observed from this study that the impact of human activity and sewage disposal in the river was severe on most of the parameters. The station located in highly urban area showed the worst water quality followed by the station located in moderately urban area and lastly station located in a moderately rural area. It was observed that the main cause of deterioration in water quality was due to the high anthropogenic activities, illegal discharge of sewage and industrial effluent, lack of proper sanitation, unprotected river sites and urban runoff.

Palaeoflood Record of High-Magnitude Events during Historical Time in the Sabarmati River, Gujarat

We report the occurrence of large floods in the Sabarmati River Basin during cal AD 1400-1440. Slackwater palaeoflood deposits have been preserved in the highly dissected ravines along the middle reaches of the river, wherein 5-6 discrete flood events have been identified. The minimum discharge that emplaced the highest deposit has been estimated as ∼15,680 m 3 s -1 and is higher than that recorded (3050 m 3 s -1 ) during the recent 2006 flood. The timing of these high-magnitude flood events in the Sabarmati and adjacent river basins suggests that extreme hydrological events have occurred in response to excess monsoon periods and are largely controlled by the regional climatic conditions. Moreover, these flood events are seen to be broadly synchronous in the alluvial river basins of Gujarat across climatic zones, but are at variance in pattern from the records of the bedrock peninsular rivers.