Impact Assessment of Water Conservation Measures: A GIS Approach

Impact Assessment of Water Conservation Measures: A GIS Approach

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Anji Reddy
Associate Professor in Environment Sciences & Technologies
Centre for Environment
Jawaharlal Nehru Technological University
Mahavir Marg, Hyderabad – 500 028
Andhra Pradesh, India
Ph: +91 40 6589706/ 3306095

Introduction
Sustainable development of rural areas involves conservation of land and management of water resources. With the increasing pressure of the ever-growing human and cattle population, increased living standards and the concomitant economic activities are exerting tremendous pressure on the finite natural resources. Due to lack of advance planning and non-judicious/indiscriminate use of natural resources, ground water levels are getting depleted and lands are getting either degraded or turning into wasteland. In India out of total 3,290 lakh ha nearly 50% of land is either waste or degraded. In Andhra Pradesh, out of 275 lakh ha of geographical area 115 lakh ha. (42%) is either waste or degraded. Andhra Pradesh Government have launched a massive 10 years watershed program for development of all degraded and waste lands during 1997 with an aim of treating 100 lakh ha of land. The Government of Andhra Pradesh has constituted Water Conservation Mission during April 2001 with the prime objective of conservation and utilisation of water on a sustainable basis.

To fulfill the aim of treating these 100 lakh ha of lands the Government of Andhra Pradesh have identified certain line departments, as below:

  • Rural Development
  • Forest Department
  • Minor Irrigation -I & CAD
  • Minor Irrigation (PR)
  • Rural Water Supply (PR)
  • Municipal Administration and Urban Development
  • Endowments Department
  • Medium Irrigation
  • Major Irrigation

The programme is being implemented in a phased manner. Each phase comprises of nearly three to four months. Three phases are already over and the fourth phase is in progress. The plans and programs of these line departments working directly or indirectly for conservation and utilisation of water are clustered together into a single programme and christened the same as Neeru – Meeru (Water and You) with the motto of promoting of water conservation on a mission basis.

Concept of ‘Neeru-Meeru’ Programme
The concept of the programme envisages creation of awareness amongst people for ensuring their participation in land and water resource management. Prioritization of the areas has been carried out to execute the water conservation & soil moisture retention activities based on the field data furnished by the state ground water department.

Stress mandals are identified based on the ground water availability and according priorities to most stress mandals of the stress mandals and areas experiencing drinking water scarcity etc. The Water Conservation Mission (WCM) acts as a facilitator and envisages to co-ordinate and guide the water conservation efforts initiated by various departments.

Adopted structures by Water Conservation Mission
The following structures are in adoption to create the additional filling space and recharge of additional ground water.

  • 61656; Continuous contour trenching, continuous peripheral contour trenching, staggered trenching.
  • 61656; Gully control works.
  • 61656; Check dams and percolation tanks, farm ponds, bunding, sunken pits, feeder channels, supply channels.
  • 61656; Desiltation of tanks, restoration of tanks etc.

In addition to these, certain districts are involved in the revival of age-old traditional water conservation practices such as:

  • The revival of age-old chain of tank systems in Srikakulam district.
  • Conversion of dried up dug wells as recharge pits through simple diversion drain techniques and
  • Installation of low cost sunken pits In the Medak District as recommended by the Technical Committee wing of the WCM.

Progress of ‘Neeru-Meeru’
During the first three phases, an additional filling space of 3068.54 La. m3 has been created with an amount of Rs. 654.22 crores. During the Fourth phase, by 12-5-2002, an additional filling space of 3478.45 La. m3 was created with an amount of Rs. 473.79 crores.

Though the government is attempting to estimate the impact of ‘Neeru-Meeru’ based on ground water levels and drinking water scarcity status, there is a need for evolving scientific impact assessment procedures for evaluation of the impact of ‘Neeru-Meeru’ works. Remarkable development in Remote Sensing and GIS and their applications in natural resources development and management have amply demonstrated and firmly established their immense potential in bringing about a transformation in the life style of the human society as a whole. Hence application of Remote Sensing and GIS particularly in carrying out impact analysis of a massive programme like ‘Neeru-Meeru’, plays a crucial role in developing scientific performance indicators for the evaluation of completed/ executed water conservative works.

Model Pilot Study
With this background, an attempt is made to carry out a pilot study by selecting a Semi arid, rain-fed drainage basin, where the government has executed considerable number of soil and water conservation activities under Neeru-Meeru programme. For this purpose, Vemuleru Watershed bearing national watershed code number: 4C4C7 as per the National Watershed Atlas is taken up as a case study.

Objectives
From the available report of Neeru-Meeru programme it is clear that the Government of Andhra Pradesh are yet evolve any scientific parameters to make systematic impact assessment of this program. Significant time has elapsed since the inception of the programme (N-M) to evolve scientific parameters so as to evaluate critically the impact of 6546.99 lac. Cum. of additional filling space created with the incurrence of Rs. 1128 crores of public money. Keeping all this in view, a systematic study is carried out with the following objectives

  • To develop scientific parameters like land use/land cover status, hydrogeomorphological conditions and normalised difference vegetation index (NDVI) based on the analysis of Remotely sensed satellite data and its integration on GIS platform.
  • To develop a comparative land use/land cover status of the selected watershed covering the years 1997 and 2001 keeping in view of the status of pre and post launching of Neeru-Meeru programme.

Methodology
The methodology adopted for the development of comparative Lu/Lc status involve the following steps:

  1. Generation of thematic maps using satellite data
    1. Land use / Land cover
    2. Hydrogeomorphology
  2. Generation of Topographic maps using SOI Toposheets
    1. Slope map
    2. Base map
    3. Drainage map
  3. Generation of NDVI using remotely sensed digital data based on red and infrared reflectance, on the basis of the expression

    NDVI = (NIR -R) / NIR + R
    Where,
    NIR = near infra red reflectance R = red reflectance.

    The variation in green vegetation density due to Neeru-Meeru programme can be analysed using the above equation.

Description of the area
Vemuleru watershed of Prakasam District in Andhra Pradesh (Figure 1) forms a part of the Gundlakamma catchments in heterogeneous peninsular shield and lies within 15o251 and 15o501 N latitudes and 79o81 and 790161E longitudes. The Vemuleru River flows from South to North and joins Gundlakamma near Nekunambadu. The area is known for recurring droughts and inhabited by a substantial percentage of people belonging to scheduled castes, scheduled tribes and weaker sections. The relevant toposheet and the two imageries (IRS-IC, LISS-III) of 1997 and 2001 are shown in Figures 2, 3 and 4 respectively.

Geology of the Area
Study area is situated in the eastern part of the Cuddapah basin. During upper Precambrian, large tracts of the area are a basin of submergence. (Chennaiah etal 1985) The formulations in this basin are a result of cyclic sedimentation and are relegated to foreland faces. Each cycle starts with a basal conglomerate, overlaid by limestone, shale and quartzite. Cumbum shales, phyllites and quartzites in the Nallamalai range are the rock formations in the study area. Ground water occurs in the intergranular pore spaces in the weathered zone and the secondary structures of the rocks of Cumbum shales and phyllites. The quartzites being massive have negligible pore space.

Climate
The study area experiences tropical and semi arid type of climate. In general, winter, low rainfall and severe summer are characteristics of the seasons. The area is classified as drought prone as the occurrence of low rainfall is more than 20 % of the years recorded (CPO (1993-1994): “Manual of Statistics”. Chief planning office, Prakasam district, Andhra Pradesh.). The average annual rainfall recorded in the area is 624 mm. Much of it is received during SW monsoon (Jun-Sept.) and NE monsoon (Oct. – Dec.) periods. As there are no major reservoirs and efficient water management techniques in practice for tapping the water, much of the rainfall drains as surface run-off.

Physiography and slope
The diversity in relief and topography in the area resulted in to two physiographic divisions. Moderately steep-to-steep sloping structural hills and plains. The eastern and western parts of the study area have steep terrain with higher relief. The Northern and Central portions are plains with nearly level slopping conditions. Distinct variations in relief, gradient, composition of material and the topography of plain areas have resulted in the formation of fluvial plains and pediplains. The slope map derived from SOI toposheets and prepared on ARC/Info GIS platform is shown in Fig.5. Seven slope categories (Table.2) are identified and later are integrated in the process of development of scientific indicators for impact study of Neeru-Meeru programme.

Drainage
The Drainage of the area is mainly dendritic to sub-dendritic in its pattern (Strahler 1952) and the basin is elongated in shape. The fine drainage density in southeast and southwest part confirms to physiography of the area, which has the lower infiltration levels. The central portion of the watershed with nearly level sloping condition depicts the medium to high infiltration rate resulting into the incremental groundwater levels. Because of the erratic nature of rainfall and impermeable nature of rocks, shallow stream channels are formed. The drainage pattern is indicated in Figure 6.

Land use / Land cover study
The satellite digital data of 1997 and 2001 are processed using EASI/PACE image processing software for its georeferencing by extracting ground control points with the help of SOI toposheet (fig.2) and the field data. (Land use / land cover field manual, Integrated surveys division, National Remote Sensing Agency, Hyderabad, A.P. India 1995) The Hard copies for the two years are generated for subsequent visual analysis of satellite data. Based on visual image interpretation of these hard copies (Figs.3 and 4), the land use/land cover maps for both the years are generated. The final land use/land cover maps are prepared on field validation with ground checks. The flowchart showing stepwise method is provided. A digital database of land use/land cover for the years 1997 and 2001 is created using ARC/info GIS software. This database is then used for impact analysis of Neeru-Meeru programme. Four broad categories of land use/land cover are identified and mapped in the study area for the years 1997 and 2001 for comparative analysis to carryout impact assessment of the Neeru-Meeru programme. The satellite imagery of 2001 exhibits an increase in area for the land use categories namely agricultural land, forestland, and water bodies. compared to that of 1997. The 2001 imagery exhibits sizeable decrease in the area of waste/degraded land. The total increase during 2001 compared to 1997 for the three classes agricultural land, forestland and water bodies is 69.59 Sq. Kms. The decrease during 2001 compared to 1997 for the waste degraded land class is around 69.59 Sq. Kms. The area statistics of land use/land cover study are presented in Table1. All the four categories of land use/ land cover patterns are indicated in Figures 7 and 8.

Topography and Ground Water status
A critical look at the topography of the study area reveals the occurrence of land form features such as denudation hills, residual hills, dykes and intermontane valley. Cumbum quartzites and dolomites are present as structural hills, whereas cumbum shales and phyllites appear as shallow to moderately weathered pediplains and intermontane valleys. The structural hill located in the SE direction covered by velikonda south reserved forest has a relief of 438 m above MSL while the one located in the SW direction covered by velikonda reserved forest has a relief of 499 m above MSL. The central portion is nearly flat occupying 39.19% of the total area. In the eastern and western portions, area has moderately to steep slopes.

NDVI Map Generation
Normalised differential vegetation index (NDVI) values are generated for the years 1997 and 2001 for the same season. The positive rise of the index is witnessed for the categories agricultural land, forest land and water bodies for the year 2001 compared to 1997. The negative index values have disappeared for the category waste/degraded land for the year 2001 compared to that of 1997. The comparative NDVI values for different land use/land cover categories for the years 1997 and 2001 are given in Table 3 The status and incremental growth of vegetation in the form of normalised difference vegetation Index (NDVI) are indicated in Figures 9 and 10.

Summary and Conclusion
A pilot study is carried out on the evaluation of impacts of Neeru-Meeru (WATER AND YOU) programme, the most popular development programme of the Government of Andhra Pradesh. This study is based on scientific parameter; NDVI and land use/land cover change detections etc. A scientific methodology is developed to monitor assess and evaluate the Neeru-Meeru programme.

The study leads to the following conclusions. Cursory examination of the land use/land cover maps depicted an increase in the areas under agricultural land, forestland and water bodies to the tune of 69.59 sq. km during post launching of Neeru-Meeru. This comparative study revealed that the soil and water conservation practices being in practice/adopted are yielding fruitful results besides other development factors.

The considerable decrease in areas of waste/degraded land conveys that the structural measures taken up have increased the soil moisture status and paved the way for rising chlorophyll status. The positive rise in the vegetative index for all the land use/land cover categories and the absence of the index values for waste/degraded class corroborates with the observations. The scientific approach through the methodology developed in this pilot study can be adopted for the overall evaluation of watershed activities elsewhere.

By adopting this scientific evaluation methodology, it will be possible for the Government of Andhra Pradesh to assess the returns for the investments made under this programme and to steer the programme in future.