IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002
million hectares (unpublished report), based on satellite remote
sensing and adequate ground truth for the period 1986 / 87.
Both water erosion and wind erosion damage can be attributed
to inadequate land cover due to deforestation or mono
cropping or overgrazing, or from farming on marginal and hill
areas.
Table-5 shows the information needs for degraded lands at
various scales of mapping and purpose for different users of
such information in the country. Though conventional soil
surveys provide such information they are slow, time
consuming and expensive. Among the new technologies
emerged for studying natural resources, space borne remote
sensing technology proved to be powerful, because of
synoptic view of the terrain features, repetitive coverage of
the same area at regular time intervals, collection of data in
visible through near infra red, thermal to microwave regions
and amenability of data to computers for quick analysis.
Necessary infrastructure has been developed in India by
various Central / provincial government agencies.
Geographical Information System(GIS) — a computer based
system for storing, updating, retrieval, analysis of data and
presentation of results is another significant development in
information technology which is proving to be helpful in
natural resources management. It also enables to develop
decision support systems by taking into account the
information available on resources at different scales, in
spatial and non-spatial formats as well as socio-economic
factors.
Remote Sensing and GIS techniques are showing their impact
on the study of environmental problems especially, land
degradation and opened up new vistas like development of
Information system that enable to efficiently assess and monitor
land degradation, through timely initiation of appropriate
strategies and measures. Survey of literature reveals that
remote sensing data from satellites like Landsat, SPOT and IRS
were employed to derive information on the nature, extent,
spatial distribution and magnitude of various types of degraded
lands like salt affected soils, waterlogged areas, ravinous lands,
eroded areas, shifting cultivation etc., and also to monitor them
periodically by various states and central government agencies
in the country.
6. REMOTE SENSING APPLICATION IN LAND
DEGRADATION STUDIES
Remotely sensed data from satellites are being operationally
used to derive information on degraded lands and monitor them
periodically in time and space domain using multi temporal
data in India ( Venkataratnam and Rao., 1977; Venkataratnam,
1980, 1983, 1984, 1989,; Venkataratnam and Ravisankar, 1992,
Rao et al., 1991; Karale et al., 1988; NRSA, 1981; Singh et al.,
1977, 1988; Sharma and Bharghava, 1987;) and in other
countries . In table — 5 the methodologies used for land
degradation assessment by different scientists / organizations
are summarized along with the input data used, scale and output
of their studies. (Table —5)
6.1 Salt-affected soils
Salt affected soils are those soils that contain excessive
concentration of either soluble salts or exchangeable sodium or
both. Depending upon the physio-chemical properties, these
Table — 5 Information Needs of degraded lands
Information RS Sensors
Scale Users
content
Nature and 1:250,000 Centre and Landsat-MSS
Magnitude of State / TM, IRS-
Salinity/ Planning LISS-I
Alkalinity, Dept./Board,
Eroded Ministry of
Lands; Types Agriculture,
of Govt. of India
Waterlogged
Areas
Refinement of | 1:50,000 Command Landsat - TM
The Area IRS — LISS-II
boundaries Development | /III
for Above Authorities /
Mentioned Watershed
Information Development
Authorities
Quantitative 1:4,000/ District IKONOS
Information 1:8,000 Implementati | Cartosat
on above on Agencies Resourcesat
Mentioned
Categories
soils are classified in to saline, sodic and saline—sodic soils. The
salt affected soils on false colour composite (FCC) prints of
satellite data appears in different shades of white tone with
smooth to coarse texture due to presence of salts (figure-1) in
the background of soils with normal crop growth.
At NRSA, the maps of salt-affected soils for entire country
were prepared at 1:250,000 scale using satellite data from
Landsat TM/IRS sensors in association with other central and
state government organizations.
Figure-1 IRS-LISS-II of 1998 FCC showing salt affected soils
(bright white patches) and water-logged areas (light to dark
bluish shades) in part of Indo-Gangetic plains in India.
According to this study, the area under salt affected soils in the
India is 6.727 million hectares and state-wise area under salt
affected soils are given in table-6. The maps of salt-affected
soils of all states are already printed at 1:250,000 scale (figure-
688
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