Terrain mapping unit of Bharatpur district
Saif ud din, Iqbaluddin and Mukhtar Ahmad
Remote Sensing Application Centre for Resource Evaluation and Geo-engineering
Aligarh Muslim University
Aligarh, U. P.
Abstract:
The surface water bodies like lakes and rivers are endangered due to indiscriminate dumping of domestic and industrial wastes. It is found that nutrients from these wastes are causing algal bloom and prolific growth of macrophytes. These can be mapped using satellite data in 0.52 - 0.59 um. Chlorophyll - a concentration is a god indicator to quantitatively estimate the presence of Phytoplankton biomass. The present case study deals with Upper Lake, Bhopal. The methodology adopted is an integration of remote sensing, conventional laboratory analysis, global positioning system and geographic information system. ILWIS 2.1 GIS package has been used in the present analysis to accomplish the task of integration and production of chlorophyll - a map of the lake.
Introduction:
Water is one of the prime necessity for the survival of any civilisation. Surface streams and lakes are the main sources of fresh water. In recent years, one of the major problem being faced by our country is the pollution of surface streams and lakes. The reasons for this are rapid urbanisation and industrialisation, as these fresh water bodies are being used for dumping the sewage and industrial wastes. There are regulations and regulatory bodies to monitor the pollution in surface streams. But they are finding it too difficult or rather impossible to implement the regulations in absence of quick and cost effective monitoring techniques. Thus, there is a need to develop a monitoring techniques for the water quality frequently and take remedial measures to preserve these fresh water bodies.
The term water quality refers to the chemical, physical and biological characteristics of water. The chemical characteristics include total dissolved solids, turbidity, colour, taste, odour, and temperature. The biological community present in the water body (Peavy et al, 1985).
The trophic status of a lake is an important aspect to be monitored frequently as it indicates the effect of incoming sewage and other wastes in it. The test to determine the trophic status of the lake is the measurement of phytoplankton biomass (OECD 1982). Lakes enriched with nutrients exhibit excessive growth of phytoplankton (Vollenwieder 1968, Harper 1992). An excess of phytoplankton can create numerous problems such as clogging the water body and reduction in the water availability for human consumption. It is observed that lake area gets depleted with dead macrophytes and total storage capacity of the reservoir is adversely affected. In addition it also hinders the recreational activities and reduces the aesthetic beauty. Phytoplankton biomass is traditionally estimated by filtering water samples and then extracting the photosynthetic pigment - chlorophyll-a.
Aim of the Study:
The conventional point sampling methods are very accurate but they are time consuming and do not display the spatial and temporal variations. In this regard remote sensing techniques, using airborne or spaceborne sensors providing multispectral and repetitive data offers a great scope for regional monitoring with the advantage of providing synoptic view and better estimate of spatial distribution.
The aim of the present study is to provide an alternate solution to conventional point sampling method of estimating water quality parameters using the tools of Remote Sensing and GIS. Here we have taken chl-a as the pollution parameter to be determined as a case study.
Study Area:
Upper lake-Bhopal make the western periphery of the Bhopal city. It is a large lake having a water spread area of 30.72 sq. km. and serves as the main source of water supply to the Bhopal city (Tamot and Srivastava, 1987). This lake has many outfalls dumping untreated city sewage and other wastes in it. From adjoining agricultural fields the fertilisers and other biomass also find their way into the lake during rainy season. These incoming wastes provide nutrients and cause algal boom.
Satellite Data:
For this study IRS-IC LISSIII image has been obtained from Nov 7, 1997 from NRSA, Hyderabad. Images of three bands i.e. band2 (0.52-0.59um), band3 (0.62-0.68um), band4 (0.77-0.86um) have been taken. The scene centre lies at 770 22' 56''E and 230 15' 00''N.
Field Sampling:
Field sampling in the lake has been conducted on Nov 7, 1997. The date was fixed keeping in mind the pass of the satellite over the study area during field sampling so that accurate relationship of chlorophyll -a with sensor records may be established. IRS-IC passes over the same area after 24 days.
Water samples were collected from various points inside the lake and brought for laboratory sampling. To accurately mark the location of sampling station inside the lake, a Global Positioning System (GPS) (SOKKIA-Spectrum) was used. Water samples from 45 different locations were collected. These samples were then tested in laboratory for chl-a concentration. The chl-a concentration has been determined by the spectrophotometric method (APHA-AWWA-WPCF, 1985).