Received Date: June 14, 2017 Accepted Date: July 24, 2017 Published Date: July 26, 2017
Citation: Mahendran V, Jagadeeswara Rao P, Bera AK (2017) Vulnerability of Different Geomorphic Units to Deserts in Parts of Western Rajasthan - A Study Based on Remote Sensing and GIS. J Remote Sensing & GIS 6: 204. doi: 10.4172/2469-4134.1000204
Copyright: ©2017 Mahendran V, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Deserts are the areas of arid ecosystem which make vegetal and animal life difficult to sustain. The process which makes desert is called desertification. It also faces the loss of fertile topsoil at desert boundaries and usually caused by a combination of drought and the over exploitation of grasses and other vegetation by people. Desert sand dunes being soft, are more prone to erosion whether wind or water. Earth Observation Technology (EOT) by use of multi-sensor polar orbiting satellites is able to provide fairly good mapping and monitoring of deserts. An attempt to explore the potential of EOT in studying desertification nexus with geomorphic units in the area of Thar desert of Rajasthan, India has done.
Deserts; Vulnerability; GIS; Remote sensing; Western Rajasthan
Cultivable land is the valuable natural resource which supports production food and fiber and many other essential goods required to meet human and animal needs for sustenance. However, it is facing serious threats of deterioration due to unrelenting human pressure and utilization incompatible with its capacity. Situation becomes more serious for the nation like India, where to cop up with agriculture production demand, large fertile land is required. A serious threat to this is desertification. Katyal and Vlek describes desertification is a condition of human-induced land degradation that occurs in arid, semiarid and dry sub-humid regions (P/PET 0.05 to 0.65) and leads to a persistent decline in economic productivity (>15% of the potential) of useful biota related to a land use or a production system [1-3]. Climatic variations intensify the decline in productivity, restorative management moderates it. Some of the main human and biotic interactions that are causing desertification hazards in the area are:
• Uneconomic land use/cultivation practice on the sand dunes, marginal lands affecting adjacent fertile lands area a means to soil erosion.
• The intensive use of water resources or it’s over exploitation leading to rise in water tables, seepage and increased salinity.
The EOT has been proven of immense help in mapping, monitoring and studying change detection of desert areas due to its capacity to cover larger area, temporal data availability, affordable cost and accuracy [4-6]. The present study focuses on delineation of major geomorphic features of the area, vulnerable geomorphic processes characterization and identification and GIS analysis for vulnerable classes of desertification.
The study area is composed of six blocks namely Ahore, Luni, Pachpadra, Pali, Rohat and Siwana of four districts Jodhpur, Pali, Barmer and Jalore of Rajasthan state. In the local language area is known as Marusthali (desertic). It is located between 25°15’N to 26°20’N latitudes and 72°E to 73°40’E longitudes. The total geographical area is 1183984.18 hectare. The area is covered in 30 toposheets prepared by survey of India on the scale of 1:50000.
The area falls under arid agro-climatic condition in Thar Desert of Rajasthan with four seasons viz., winter, summer, monsoon, and post monsoon. The climate of the region is hot and dry. Rainfall received is very less, the temperature is very high all around the year and all these conditions generate an arid to semi-arid picture of the area. The temperature variations are also great.
The temperature begins to rise from the month of March and May reach up to 50C occasionally particularly in the Barmer district during the June and July. High temperature may be associated with high-speed dust storms, which are normal in the month of April and May. Even in the winter season also the daytime remains quite hot. The received sunshine per day is around 9 hours. This can be given as the reason of high temperature because when sunrays fall on the sand it become hot and raise the surrounding temperature. The mean maximum summer temperatures (may) range from 40°C to 42°C. During winter (December to February) the mean maximum temperature ranges from 15°C to 25°C and the minimum temperature slash down to the freezing point. The average annual rainfall received in the area is about 278.78 mm (Figure 1).
Land use and land cover of the study area is done with ETM 2000 of LANDSAT Satellite data and IRS LISS-III 2006 of all the three-season data viz., Kharif, Rabi and Zaid (Table 1). The classification scheme adopted for present study includes six classes at level-I and twenty-two classes at level-II. On the basis of land use and land cover area can be broadly classified as agriculture land, built up land, forested land, waste lands and water bodies as per level-1 land use\land cover classification system developed by NRSA. During 2000, about 32.45% area was under fallow land followed by 20.09%, 3.95%, 3.15%, 33.02% area under crop, land with scrub, land without scrub and sandy desertic (Figure 2). The forest area is very less.
|LULC: Level – I||LULC: Level-II||Area (ha)||% of Study Area|
|Wasteland||Land with scrub||46755.62||3.95|
|Land without scrub||37328.88||3.15|
|Water bodies||River with water||717.24||0.06|
|Salt Basin||Salt basin||6273.41||0.53|
Table 1: Landuse/Landover Categories in Year - 2000.
During 2005-2006, the areas under various land use/land cover categories changed considerably (Table 2). About 32.42% of total area was under fallow land followed by 9.92%, 4.75%, 0.66%, 3.33%, 0.22%, 0.53%, and 0.70% area under only kharif, only rabi, only summer, kharif and rabi, kharif and summer, rabi and summer and all the three kharif, rabi and summer [7,8].
|LULC: Level – I||LULC: Level-II||Total Area (ha)||% of Total Study Area|
|Built –up||Urban settlement||2206.39||0.19|
|Wasteland||Land with scrub||46915.00||3.96|
|Land without scrub||37423.35||3.16|
|Salt basin||Salt basin||6274.37||0.53|
Table 2: Landuse/Landover Categories in Year - 2005-06.
An assessment of change in area under various land use/land cover categories during 1999-2000 to 2005-2006 revealed that agriculture area increased by 263.25 ha. The wastelands decreased by 136.17 ha because the decrease noticed in the sandy desertic and due to various reclamation measures taken by farmers. However, there is marginal decrease (9.08) in surface water resources (Figure 3).
Land degradation assessment
The increasing human and livestock population pressure over the last decade has disturbed the ecological balance of study area to a considerable extent. As a result, many areas have converted into degraded land. The severity classes find in the area are identified viz., slight, moderate and severe for all wind, water and salinization processes (as per NRC Land Degradation Manual). The major processes of degradation active in the study area are wind erosion, water erosion and salinization. As it falls in the desert, the wind erosion is much more prone then other categories. Area affected by wind erosion process (slight) covers 1.23% of Ahore block, followed by 2.42% in Siwana, 12.27% in Pachpadra and 10.97% in the luni area respectively.
About 3692.30 ha (1.76%) of Siwana, 10937.55 ha of luni (5.66%) and 7171.63 ha (2.08%) area of Pachpadra blocks, respectively are degraded by wind erosion process with moderate severity. The area affected by wind erosion severe is 951.65 ha (0.59%) in the ahore block, 4586.26 ha (2.19%) in Siwana block, 7916.08 ha (2.30%) in Pachpadra block, 6901.61 ha (3.57%) in luni block, 3256.81 ha (2.49%) in Pali block and 2709.28 ha (1.91%) in the Rohat block. Wind erosion process, in general, affected both agricultural and wastelands. The sandy patches may be in situ or transported in origin. Windblown sand dunes support vegetation where moisture available. Water erosion process (severe i.e., formation of ravines) was more predominant in ahore block where 4.24% of block area is degraded by it, followed by 2.58%, 2.32%, 2.30%, 2.19% and 1.02% areas under Pali, Rohat, Pachpadra, Siwana and Luni blocks respectively. Water erosion is a major process of land degradation both in arable and non-arable lands. However, ravine formation is generally observed in barren lands along river or drainage network due to high intensity rainfall and subsequent rapid runoff. In some of the blocks the moderate and slight water erosion is also observed (Table 3).
|Block Name||Process of Degradation-Severity||Area (ha)||% of Corresponding Block Area|
Table 3: Area affected by various degraded processes in different blocks.
Salinization process (moderate) affected only one or two blocks small area (22413.06 ha) of Pachpadra block, which is 6.52% of the block area and 0.87% (1683.74 ha) area of the luni block. In the part of Siwana slight salinization is also noticed which is 2.17%. Salinization process is active mostly in unirrigated agricultural land and scrublands. Salinity development has been taken place due to inherent limitation or brackish groundwater and its subsequent capillary rise to the surface in the part of Pali and Ahore blocks. In the Pachpadra block one salt basin is also present that is known as Pachpadra salt basin. It covers the total area of 6275.45 ha of the block (1.82%).
Changes in land use/land cover pattern during 1999-2000 to 2005- 2006 are evaluated (Table 4). Although the change is not that much varied. Changes in the directions namely degraded wasteland categories to cropland, water bodies and plantation etc., has been considered as ‘positive change’. About 1032.02 ha have been improved because of ‘positive change’. Changes in the reverse direction namely, fallow land to wastelands; forest to wastelands; dry water bodies to wastelands etc. have been considered as ‘negative change’. Area degraded due to negative changes covers about 279.31 ha which is almost negligible (Table 5). Parts of the remaining area have undergone changes but those can’t be regarded either positive or negative. About 11832672.84 ha belong to ‘no change’ category (Figure 4).
|LULC: Level – I||LULC: Level-II||Total area based on Landsat data (ha)||Total area based on IRS LISS – III data (ha)||Change in Area (ha)|
|Built –up||Urban settlement||2120.05||2206.39||81.95|
|Wasteland||Land with scrub||46755.62||46915.00||159.38|
|Land without scrub||37328.88||37423.35||94.47|
|Salt basin||Salt basin||6273.41||6274.37||0.96|
Table 4: Change in area under various land use/land cover categories during 00 to 05-06.
|Change Type||Area (ha)|
Table 5: Type of changes in land use/land cover during 2000 to 2005-06.
Vulnerability of geomorphic units
The vulnerability of different geomorphic units on the basis of weathering resistant capacity (bearing capacity), water erosion severity, wind erosion severity, vulnerable water erosion classes, vulnerable wind erosion classes with other collateral data like soil erosion, slope etc. is prepared. The classes viz., high, moderate and low are made on this basis. This table shows that dune field, aeolian plain, valley fills, flood plain and piedmont slope aeolian show the high vulnerability to the land degradation and desertification in the particular area of Thar desert. All the geomorphic units consist of igneous rocks shows low to moderate category because of hard and compact nature of the rock and high resistance capacity like-pediment volcanic, pediment granite etc. The geomorphic units like pediment volcanic, denudational hill volcanic show the low category because of their hard and compact nature.
Table 6 also shows the reverse relationship between bearing capacity of the rock and vulnerability level. The softer the geomorphic unit, greater the activeness of the erosion activity in the case of wind. In the case of water, it depends upon the chemical reaction. According to the table dune field having the low bearing capacity and thus the vulnerability level is high. In the case of denudational hill volcanic bearing capacity is moderate to good but the vulnerability level is low.
|S. No.||Geomorphic Unit||Erosion Resistant Capacity||Vulnerability Level|
|5.||Pediment Volcanic||Moderate to good||Low|
|6.||Denudational Hill Sedimentary||Moderate||Low|
|7.||Denudational Hill Volcanic||Moderate to good||Low|
|8.||Pediplain Granite||Moderate to good||Low|
|13.||Playa||Low to moderate||Moderate|
|16.||Flood Plain||Low to moderate||High|
|18.||Pediplain Phyllite||Low to moderate||Moderate|
|20.||Pediment Granite||Moderate to very good||Low|
|21.||Denudational Hill Granite||Moderate||Low|
|24.||Peidmont Slope Eolian||Low to moderate||High|
Table 6: Relationship between bearing capacity of the rock and vulnerability level.