Sachin Panhalkar
Lecturer, Department of Geography, Shivaji University Kolhapur, Maharashtra,
panhalkarsachin@yahoo. co.in
C. T. Pawar
Former Prof. and Head of Geography Department, Shivaji University Kolhapur, Maharashtra.
Abstract
Land use /land cover change (LULCC) is a general term for the human modification of Earth’s terrestrial surface. Though humans have been modifying land to obtain food and other essentials for thousands of years; current rate, extents and intensities of LULCC are far greater after the introduction of irrigation projects. Hence, it is of prime importance to assess the land use/ land cover changes with respect to the development activity like irrigation. The region selected for the present study is Chikotra basin of south Maharashtra. It is located between 16° 5’48’’ to 16° 19’ 32’’ north latitudes and 74° 4’ 25’’ to 74° 17’ 48’’ east longitudes occupying an area of 29,076 hectares. The study was carried out using IRS 1C, LISS III data of February 25, 1991 (pre-treatment) and IRS P6, LISS III data of February 14, 2008 (post-treatment) covering the watershed to assess the changes in land use / land cover for which supervised classification technique has been applied. NDVI index is also calculated to assess biomass conditions and post classified change detection technique is used for accurate detection and efficient analysis of changes during the period of investigation. The analysis reveals that only 16.16 per cent of additional land has been brought under irrigation. The overall assessment of the irrigation project is not satisfactory as only 60 per cent target area has been achieved through completed projects.
1. INTRODUCTION
Irrigation is a vital factor for development of agriculture, especially in India, where the natural source of water, that is, monsoon rainfall, is highly variable in amount and distribution. In spite of the large investments made in the irrigation sector in India and the phenomenal growth of irrigation potential since the year 1951, the returns from the investments are disappointing (WTC, 1983). The reason for the poor performance of the Irrigation projects is due to the fact that the emphasis has been given to construction of new projects rather than the management of irrigation projects. Hence, regular monitoring of LULCC is needed to improve water management. Improved water accounting is required to track agricultural and nonagricultural water use, particularly in irrigation. Most of the LULC classification efforts in the past three decades used single or a selected few remote sensing images (Foody, 2002). Such classifications provide little or no information on the temporal dynamics of LULC classes, highly limiting their use (DeFries & Los, 1999). In recent years, AVHRR pathfinder time-series images (for example, DeFries et al., 1998; Loveland et al., 2000) have been used to capture temporal dynamics of LULC at global level. However, it is only recently that near-continuous time series images from sensors such as Moderate Imaging Spectrometer (MODIS) on board NASA’s Terra and Aqua satellites have allowed assessment of LULC dynamics and quantitative landscape characteristics (Huete et al., 2002) in near real time. Comparison of two times classified outputs and Normalized Difference Vegetation Index (NDVI) images using change detection software can be performed to study the land cover and vegetation vigour transformation (Singh, 1989; Fung, 1990). The main objective of the present study is assessment of the irrigation development in the Chikotra basin through land use/ land cover and biomass change analysis.
2. MATERIALS
2.1 Study Area:
The study area lies in the southern part of Kolhapur district, Maharashtra and mainly covers a part of Bhudargadh, Kagal and Ajara tahsil. It lies between 16° 5’48’’ to 16° 19’ 32’’ north latitudes and 74° 4’ 25’’ to 74° 17’ 48’’ east longitudes occupying an area of 29,076 hectares (Fig. 1). Physiographically, the study area comprises of hills on the southwestern side and plain area on the northeastern side forming irregular and diverse nature of topography.
Fig-1: Location map of study region
2.2 Methodology:
To assess the irrigation development in the Chikotra basin through land use/ land cover and biomass change analysis, the recent techniques like remote sensing and GIS have been applied.
IRS 1C, LISS III digital data of February 25, 1991 is used along with IRS P6, LISS III data of February 14, 2008 to assess the changes in land use / land cover that have changed over a period of 17 years. The digital data was preprocessed and geo-referenced to remove systematic and nonsystematic errors. The digital classification was based on the widely popular supervised classification technique, the maximum-likelihood classifier. This needed a number of training sites for all the classes spread across the study area to capture spectral variability. Separability analysis was undertaken using diversion matrix on training data to understand the separability between different classes in spectral space. The confusion matrix was derived for digital analysis of LISS III data. At last, the images were classified into six different land use/land cover categories.
They were also classified into different biomass levels using Normalized Difference Vegetation Index (NDVI) approach. The classified data was transferred to a GIS platform (ERDAS), and change detection was done using post classified method.
2.3 Irrigation Development:
During the period under investigation (1991-2008), one medium and four minor projects have been completed in Chikotra basin (Table 1). These projects are basically planned to enhance lift irrigation facilities for 7740 hectares of land for agriculture development. The total cost incurred to complete these projects is around INR 152.52 crores.
Table -1: Medium and Minor Irrigation Projects (1991 to 2008)
3. RESULTS AND DISCUSSION
3.1 Land Use /Land Cover Change (LULCC) Analysis:
The land use/land cover pattern of a region is an outcome of natural and socio–economic factors and their utilisation by man in time and space. Land is becoming a scarce resource due to immense agricultural and demographic pressure. Hence, information on land use / land cover and possibilities for their optimal use is essential for the selection, planning and implementation of land use schemes to meet the increasing demands for basic human needs and welfare. Land use and land cover change has become a central component in current strategies for managing natural resources and monitoring environmental changes. According to supervised classified images (figure 2 and 3), six classes were identified and the changes in land use /land cover are represented in Table 2.
Fig-2: Supervised classified image IRS 1C (Pre-treatment)
Fig-3: Supervised Classified image of IRS P6 (Post-treatment)
In Chikotra basin, out of the total geographical area, about 60.19 per cent was under cultivation (Net sown area and fallow land) which has remained unchanged in 2008 (60.01 per cent). The substantial change can be observed with respect to fallow land as it has been decreased by 16.34 per cent during the period under investigation. The analysis reveals that fallow land areas have been brought under cultivation. It might be a result of enhanced irrigation facilities. The lower reaches of Chikotra basin is having high proportion of agricultural land and low proportion of fallow land and the vice versa situation has been observed in the upper reaches of south western high altitude areas of the basin in 2008. The south western part of the region which is dominated by Western Ghats is having dense forest and grassland. The area under forest and grassland has decreased by 1.52 per cent, especially in western and southwestern hilly tracks of the basin during 1991 to 2008. It shows that the natural resources of this basin are not sustainably managed as the actual dense forest is about 5.06 per cent only. The barren land share is about 27.47 per cent. It has increased by 3.19 per cent. Relatively high proportion of this category is confined to degraded hilly and plateau areas of Budargadh tahsil and lower reaches of Chikotra basin of Kagal tahsil. The proportion of water bodies, which includes dam, tank and rivers accounts for 0.74 per cent. This has shown 0.48 per cent increase which is a good sign of improved water harvesting facilities. During the period of investigation, the Chikotra basin has observed a substantial LULCC.
Table 2: Land Use/ Land Cover Change (1991-2008)
3.2 Impact on Biomass:
The normalized vegetation index (NDVI) analysis was used to detect the spatial and temporal change of vegetation biomass in the study area. The collection of accurate, timely information of vegetation is always important (Groten, 1993).The collection of such information is expensive, time consuming and often impossible (Eastman and Fulk, 1993). Hence, an alternative is the measurement of vegetative amount and condition based on an analysis of remote sensing spectral measurement. The Normalised Difference Vegetation Index (NDVI) gives a measure of the vegetative cover on the land surface over wide areas. Here, by applying this technique in conjunction with change detection analysis the impact of past irrigation programmes on biomass has been assessed.
3.2.1 NDVI Formula:
NDVI = (NIR – VIS)/ (NIR + VIS) (1)
Where NIR=Near Infrared
VIS= Visible Red
3.2.2 NDVI Index and Change Detection Analysis
The NDVI index of Chikotra basin has been calculated for two consecutive images (IRS 1C LISS III and IRS P6 LISS III) for the same season. The NDVI values of IRS 1C LISS III (Pre treatment) and IRS P6 LISS III (post-treatment) image ranges between -1 to 0.76 and -0.30 to 0.57 respectively. A higher value shows the high vegetation areas like forest, which is basically confined to southwestern hilly areas of Chikotra basin. The cultivated fields also show quite high NDVI values as compared to fallow lands, which are basically confined along the Chikotra River. Water bodies are having negative index which is observed at dam and tank site. The status and impact of various watershed projects in the form NDVI is indicated in Figures 4. The degraded hilly areas of Kagal tahsil are having very low NDVI index, as these areas lack in vegetation cover. The completed irrigation projects have shown satisfactory results along the river basin, as net sown area has increased on one hand and fallow land has decreased on the other. The degraded hilly areas are not benefited through these projects as they have not shown any substantial change. The accurate detection and efficient analysis of changes between time series images are very complicated processes for users rapidly moving from massive image to meaningful information for decision making, including accurate processing of temporal images, synoptic and compared views at varied spatial and temporal scales, and searching changes at large coverage (Singh A., 1989). Negative impact is clearly observed as the dense forest has suffered degradation. It is the result of increased human intervention through agriculture, settlement and other activities. The lower reaches of Chikotra basin have high proportion of agricultural land which shows positive NDVI values. To some extent, the facilities of irrigation along the river basin have improved as a result the area under cultivation along the river basin has increased. The lower value shows non vegetation areas like barren land, fallow land, water bodies, settlement etc. At few places, the negative index values have disappeared for the category waste/degraded land for the year 2008. It is observed through Change detection analysis (Fig. 5) but still the impact is not satisfactory enough.
Fig -4 NDVI Index of Chikotra Basin (Post- treatment)
Fig -5
Here the study reveals that the results are not up to the desired level like other large-scale irrigation development project of India (GOI 2002). As the main objective was to bring 7740 hectares of command area under irrigation but the LULCC analysis reveals that only 4698 hectares of additional land has been brought under irrigation. This is not a positive sign of Irrigation development. It shows that only 60 per cent target is achieved.
4. CONCLUSION
During the period of analysis, the substantial LULCC has been observed in Chikotra basin. The net sown area has been increased by 16.16 per cent. However, the percentage of follow land has decreased by 16.34 per cent. This change is a result of improved irrigation facility through completed irrigation projects. The change is specifically confined along the river course. The hilly areas of Kagal tahsil have not shown any substantial change as the NDVI index of these areas are below 0.10. The satellite images of study region acquired during 1991-2008 periods have offered a rich source of information about changes in land use /land cover and NDVI index in the watershed over a period of 17 years. The Irrigation projects implemented during the period of analysis were not found financially viable as only 60 per cent target area is achieved through completed projects.
ACKNOWLEDGEMENT
The authors are very much thankful to UGC (New Delhi) for providing financial support, which made this work possible.
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