Shirishkumar S. Gedam

GPS derived spatial ionospheric total electron content variation over South-Indian latitudes during intense geomagnetic storms

The geomagnetic storms are turbulence in geomagnetic field when interplanetary magnetic field driven by solar wind move southward and continue for extended period of time. Although these occur less frequently, but may energize ionospheric electrons and particles adversely affecting ground- and space-based electronic systems. Ionosphere at higher latitude is more prone to geomagnetic storms. Over lower latitude region like Indian sub-continent, the effect is less prominent but still can exhibit many distinctive effects like scintillations, equatorial ionization anomaly, fountain effect and equatorial electrojets. The increased numbers of free electrons in ionosphere introduce delays in global positioning system (GPS) satellite signals resulting in errors during GPS positioning. In a dual frequency GPS receiver, the line integral of free electron density along the pathway of signal through the ionosphere (i.e., Total Electron Content, TEC) can be measured. In this present paper, GPS observation data of three low latitude GPS stations in India located at Bangalore, Hyderabad and Mumbai during four severe geomagnetic storms from 2003-2005, are processed to measure ionospheric TEC during the events. The measured TEC at each of the station is compared with quietest days of the months to investigate its abnormal changes in responses to severe geomagnetic storms. The consequences of TEC variation is analyzed and correlated with interplanetary magnetic field (IMF-Bz), geomagnetic Kp and Dst-indices to study its behavioral changes during the storms. Eventually the aim of the study is to estimate the influence of ionospheric condition on GPS positioning to devise suitable method for accurate position measurements in the low latitude Indian region.

Effects of urbanization on river basin ecosystem - A framework

Sub-tropical river basins are one of the complex ecosystems and are said to be self-sustaining if left undisturbed. But due to rapid urbanization, unplanned infrastructure developments and over exploitation of the natural resources, these river basins are under extreme pressure especially in terms of water resources. Altered hydrology is a characteristic of urbanized river basins. Therefore, for sustainable river basin ecosystem management, the inadequate knowledge about the factors influencing the river basin ecosystems is one of the major problems. Some conventional methods used for such studies include analysis of the data collected from gauge stations, surveying and sampling method which ultimately leads to the development of statistical models. These models are able to establish the correlations between some factors but they are not functionally viable. For effective river basin ecosystem management, a model is required by the planners to understand the hidden correlations between the factors affecting the urban river basin ecosystem. This paper describes a framework model to study the effects of urbanization on river basin ecosystem using geospatial technologies. To perform the study at regional scale, an attempt has been made to integrate the geospatial data with hydrological, meteorological and environmental data. The results will help to understand the effect of spatio-temporal land use land cover change dynamics on the ecosystem of a rapidly urbanizing sub-tropical watershed.

Implications of demographic changes and land transformations on surface water quality of rural and urban subbasins of Upper Bhima River basin, Maharashtra, India

For sustainable development in a river basin, it is crucial to understand population growth–land use/land cover (LU/LC) transformations–water quality nexus. This study investigates the effects of demographic changes and LU/LC transformations on surface water quality of rural (Ghod) and urban (Mula-Mutha) subbasins of Upper Bhima River basin. Population data (1981–2011) and LU/LC data {October 2002 [Landsat Enhanced Thematic Mapper (ETM+) data] and October/November 2009 (Indian Remote Sensing 1C Linear Imaging Self Scanner III data]} were analysed using statistical, remote sensing and geographic information system techniques to study demographic and LU/LC changes, respectively. Further, overall indices of pollution (OIPs) developed specifically for rural subbasin (OIPr: Hardness CaCO 3 and Total Dissolved Solids), urban subbasin (OIPu: Biological Oxygen Demand, Chlorides, Coliform Total, Colour, Dissolved Oxygen%, pH and Turbidity) and single OIP considering all parameters (OIPa) were used for spatio-temporal water quality assessment of pre-monsoon and post-monsoon periods. Results revealed that from 1981 to 2011, population increase was higher in urban subbasin than in rural subbasin. Subsequently, from 2002 to 2009 mainly increase in built-up lands (3.82%) and agricultural lands (15.35%) in urban and rural subbasins respectively, affected their water quality. From 2002 to 2009, the highest increase in OIPr and OIPu was observed at Kashti (3.37–6.52 due to fertilizers) and Bundgarden Bridge (3.03–7.83 due to municipal and industrial wastes) stations of rural and urban subbasins, respectively. With significant increase in OIPa of 2.74–6.70, Bundgarden Bridge station affected by urbanization had the most polluted water quality.

Spatiotemporal Variations in the Precipitation Deficit and Groundwater Recharge Deficit of Mula–Mutha Watershed, Maharashtra, India

The Mula–Mutha watershed of Maharashtra, India, is under chronic water shortage since past few decades. Due to uneven distribution of rainfall across the watershed, majority of its population are reliant on groundwater resources for its domestic and agricultural demands. In this study, an attempt is made to investigate the spatiotemporal variations in the precipitation deficit and groundwater recharge deficit of Mula–Mutha watershed using the Standardized Precipitation Index (SPI) and Standardized Water-Level Index (SWI), respectively. These variations are studied by generating SPI and SWI maps in geographic information system (GIS) environment for two seasons, viz. pre-monsoon (May) and post-monsoon (October), of the years 2001–2010. This paper helps to identify the groundwater stress zones across the study area where proper management of groundwater resources is required. Results reveal that in the Mula–Mutha watershed hydrologic stress varies highly in time and space. Few zones are identified where groundwater stress is more frequent. There are no regular spatiotemporal patterns observed in the precipitation deficit and groundwater recharge deficit across the region.

Remote sensing and GIS based impact assessment of land transformations on ground water level of a rapidly urbanizing watershed of India

Rapid urbanization changes the surface and sub-surface hydrological characteristics viz. Land Use/Land Cover (LU/LC) and Ground Water Level (GWL) of the watershed. Upper Bhima watershed of India is highly stressed in terms of water resources due to uneven distribution of rainfall and increasing urbanization. For sustainable development in this region, it is crucial to understand the impact of land transformations on GWL. Geospatial technologies viz. remote sensing and Geographical Information System (GIS) serve as efficient aids in assessing these impacts of sustainable development in a watershed. In this study, time series satellite datasets of 2002 and 2009 are analyzed to evaluate LU/LC changes. Whereas, Standardized Precipitation Index (SPI) and Standardized Water-Level Index (SWI) are used to understand the precipitation deficit and ground water recharge deficit for the period of 2002-2009 respectively. From results, it is observed that LU/LC is changing rapidly, which is highly affecting the GWL of the Upper Bhima watershed.

Effects of land use/land cover changes on water quality of a sub-tropical river basin

Uncontrolled urbanization results into sudden and rapid changes into Land Use/Land cover (LU/LC) of a subtropical river basin. Water quality is an important indicator of river basin health. For better river basin planning and management, the information is required on the state of water quality and the changes occurring into it. Remote Sensing and GIS are efficient aids for such study. Water quality parameters such as pH, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Nitrate, Nitrogen (total oxidized), Electrical conductivity (EC) and Fecal Coliform Bacteria, at different sampling stations across the Upper Bhima river basin were analyzed to monitor the water quality changes in the basin. It is attempted to find if any relationship exists between the LU/LC changes and water quality of the river basin. Results reveal that LU/LC is changing rapidly in the study area and is strongly related with changes in water quality parameters.