The methodological framework for the present study encompasses interpretation of satellites imageries followed by ground truthing and ancillary information for final analysis. Multi-temporal satellite images and Cartosat Digital Elevation Model (DEM) were used to develop the future land use/cover thematic maps. The LANDSAT series multi-temporal satellite images of the study area were obtained from the official website of the US Geological Survey (https://earthexplorer.usgs.gov/). Table 1 shows the details of the images that were obtained.

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Misleading Color Composite (FCC) photographs were used for supervised classification to decrease issues with visual perception of land use/cover classes training regions. The input data was pre - processed and prepared for land use/cover prediction using ERDAS Imagine and ArcGIS software. “Landsat imagery is recommended for its good precision and near and mid-infrared bands, that also enable detailed analysis of vegetative cover and landscapes”. The images were chosen based on their availability and quality from four cloud-free ETM+ for 1991, Landsat 4, 5 (TM) for 2001, Landsat 4,5 (TM), and Landsat 8 satellite data for 2021. Image enhancement, Extraction, georeferencing, layer stacking (band selection and combination), topographic correction, were among the standard image processing techniques used.

The USGS Level 1 Land Use/Land Cover classification method was employed in this study. Six unique classifications were utilized to order the research region. The classes are depicted top to bottom in Table 2. These classes were distributed to pixels in picture order. Surface, tone, and shading were utilized to make each class. Utilizing multi-worldly Landsat photographs of the review region, land cover types were considered and arranged.

Following the supervised characterization, the essential post-processing was finished. The LULC change study was assessed using pair-wise correlation and weighted overlay in the Arc GIS 10.3 environment. In light of the ground approval, the proper alterations and changes have been performed. To investigate the primary changes, the region in hectares and rate changes somewhere in the range of 1991 and 2001, 2001 and 2011, and 2011 and 2021 were measured for each LULC type. On account of their minimal expense and excellent temporal resolution, remote detecting and GIS-based change recognition approaches are generally utilized. The post arrangement examination approach, which depends on greatest probability directed order, is the most broadly involved technique for distinguishing LULC changes. The post-characterization comparison procedure includes arranging photographs and endeavoring to contrast the connecting classes all together with recognizes districts of progress.

Horticulture, Waste Land, Built up Land, Forest Land, and Water Bodies were characterized as Land Uses in the arrangement layout delivered. Out of 4160 sq. km of the watershed the agricultural land is the most dominant category which covers more than 48.38 % of the watershed. The next dominant class in the watershed is the forest cover area which covers about 39.54 % of the watershed. The built-up area tends to be increasing from 2.8 % to 10.20 % over last few decades whereas forest cover shows very minute fluctuations in the past few years. Grassland also showed a declining trend from 0.19 % to 0.09 % of the watershed. Whereas the major category of the watershed i.e. water bodies increased from 0.42% to 1.05%.

The Table 2, below shows the areas of coverage of various categories of land use in the watershed from 1991-2021. The agricultural land seemed to decline in last 40 years gradually. The agricultural land covers the maximum area of 2253.67 sq. km i.e. 54.17% in 1991 which declined to 2012.18 sq km i.e. 48.38 % in 2021. The change percentage in agricultural land is 5.79%. The highest change is seen in built up land which increased by 7.36% followed by agricultural land which is declined by 5.79 % in the four decade. The grassland or grazing land is seen to have slight change of 0.1% whereas forest cover and water bodies also showed a slight change of 2.54 and 0.63 respectively. The wasteland cover has also detoriated from 229.63 sq. km in 1991 to 37.11 sq. km in 2021. The Arkavathy watershed was subjected to significant land use changes during three time periods (1991–2001, 2001–2011, and 2011–2021), according to the land use trend analysis.

During this period, the coverage of agricultural land was highest which covers an area of 2253.67sq km i.e. 54.17% in 1991 followed by forest cover. Forest covers about 37% of the watershed in 1991 which slightly increased to 37.23% in 2001. On the other hand, both built up area and water bodies have increased by an aerial coverage of 144.9 ha (3.04%) and 17.65 ha (0.42%), respectively. Furthermost, grassland and wasteland declined at an expanse of 1.99 ha (0.04%) and 57.03 ha (1.37%) respectively. Consequently, there was a rapid conversion of agricultural land to build up areas.

The table below shows the change that happened in land use from 2001-2011. In the mid-decade there is a very slight change of 0.72% seen in agricultural land whereas the built-up area is seen to increase every year. A total of 1.45 % built up area has increased in between 2001-2011. There is a slight negative decline of 0.02% and 1.76% is seen in grasslands, wastelands respectively. There is no much change seen in forest cover and water bodies as well. The major land cover in the watershed is agricultural land which covers about 50.73% in 2011 whereas grassland covers the least area of about 4.93 ha. Built up area has increased from 263.44 ha to 323.98 ha. The developed region, which is generally possessed by Bangalore City and is shown in red, is for the most part noticeable on the north eastern side of the watershed.

The results of the year 2021 compared to that of the previous year remained almost constant. The agricultural land declined from 2110.4 ha in 2011 to 2012.18 ha in 2021 whereas the built-up area has increased from 323.98 ha to 424.68 sq. km (10%) in 2021. The agricultural lands, grassland covers and wasteland has showed negative trend with 98.22%, 0.83% and 62.26 % respectively. The wasteland has detoriated from 99.37 ha to 37.11 ha which showed 62.26% of negative decline in wasteland cover. The grassland cover is seen to decline 4.93 ha in 2011 to 4.12 ha in 2021. The grassland covers only a small area in the watershed whereas built up area showed a positive increase in its land cover from years and is still tend to continue. The built-up area has doubled in between 10 years from and the maximum change is seen to be in this class whereas in the last decade grassland and water bodies showed a very minute change in the watershed. The waste lands and grasslands were converted to satisfy the increasing demands of human population.

The watershed appears to have undergone significant alterations in most land-cover types and years. According to satellite photos of the Arkavathy watershed from 1991 to 2021, agricultural land covers 54.17 percent of the area in 1991, making it the watershed's most populous land cover. But in 2021 the agricultural land cover decline to 48.38% which showed a negative decline of 5.79% in a span of 40 years. The built-up land or the settlement areas have increased by 7.36%. The built-up area is mostly concentrated near Bangalore Metropolitan Region which covered an area of about 118.5 sq. km in 1991 which later increased to 424.68 sq. km in 2021. The forest cover didn’t show much change in the four decades. The grassland and wasteland showed a slight negative decline of 0.1 and 4.62 % in that period of time respectively. There is an increase in water bodies. The water bodies spanned an area of roughly 17.72 square kilometers in 1991, which expanded to 43.71 square kilometers in 2021.

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To sum up, the land use of Arkavathi watershed has undergone drastic change in last four decades from 1991-2021 as a significance of normal growth of population and abnormal growth of urbanization. This research is critical in understanding land invasion in many land categories. The multi-temporal satellite photos were also crucial in quantifying the watershed's geographical and temporal features. Due to rising population and need for settlement, profitable agricultural land is being converted into built-up areas. There is a continuous deterioration of agricultural land cover and grassland in the watershed. This study reveals that and its surround areas. The increasing anthropogenic activities and settlements and declining of natural vegetation cover in the watershed is a major concern. Moreover, the expansion of Bangalore city is having another serious impact on the watershed and other major land covers. The whole arrangement of changes is the result of a complicated cooperation between different causes. As a result, making informed decisions for sustainable resource development and environmental conservation strategies for a better tomorrow is critical in order to prevent land use and land cover from further degradation.