NDWI and, NDVI of the Meghadrigedda Sub-Watersheds for Optimal Utilization of Resources, Visakhapatnam District, Andhra Pradesh-India Using Landsat Data 2000 and sentinel Data 2020

With global warming and over-exploitation of water resources due to population explosion and related issues, numerous studies are being carried around the world in an effort to reinstate a state of a balanced life between the existing water resources and their utilization by human beings. Keeping in view, a watershed of 366 sq.km on 1:50,000 scale 65O/1 SOI map surrounding the Meghadrigedda reservoir in Visakhapatnam district of Andhra Pradesh, India has been taken up for the study. The watershed has been delineated into nine sub-watersheds and hydrogeomorphology, drainage, drainage density, slope, NDVI and NDWI of the study area has been carried out using Landsat data 2010 and Sentinel data 2020 in ARCGIS 10.0 environment. All the villages in the catchment greatly depend on groundwater for irrigation, drinking as well as personal utilization. Change detection has been carried on to display the decline in surface water and ground water due to increased concentration of built-up land, siltation of ponds as well as decrease in the number of ponds. The watershed is experiencing large scale anthropogenic activities. The government must curb built-up activities and desilt the ponds to sustain the monsoon water, facilitating more recharge. The results of the study can serve as a basis for planning as well as for the development of a sustainable basin area.


Introduction
Remote sensing technology has opened up avenues in groundwater prospects exploration and management. Satellite images are increasingly used in ground water exploration because of their utility in identifying various ground water features which may serve as either direct or indirect indicators of the presence of groundwater [1].
Water, the most important natural resource which obviously forms the core of our ecological system on this earth has been abused by the human population over generations.
Around 70% of India's population is directly or indirectly dependent on agriculture-based economy and availability of water resources is a prerequisite to it.
According to a report published by the central water commission (CWC) in 2001 [2] the state of Andhra Pradesh is having a total of 1157 watersheds, out of which 106 are overexploited and 79 are in deteriorating condition. It is understandable that optimal utilization of water resources is a key to the sustenance of the future economy. In this context the importance of water has been recognized and greater emphasis is being laid on its economic use and better management.
Spatial data distribution of surface water is a support system for numerous scientific activities, agriculture, Industry etc. The hydrogeomorphology, lineament mapping of the watershed along with evaluation of groundwater prospects in the watershed have been attempted by delineating the study area into nine sub-watersheds and hydrogeomorphology, drainage, drainage density, slope, NDVI and NDWI of the study area has been carried out using Landsat data 2010 and Sentinel data 2020 in ARCGIS 10.0 environment. Good groundwater prospects dominate the area showing moderate to excellent potential.

Review of Literature
Satellite technology is well established in the field of water resources by eminent authors, studies in Visakhapatnam were carried out for the development and major groundwater resources using multi schematic approach based on remote sensing studies are recommended optimal land utilization and farming techniques in Pendurthi mandal, Visakhapatnam district, Andhra Pradesh India, A Geo spatial approach (2020), [

Physiography and Study Area
The study area lies within the geographic coordinates of 17˚47' 29 Geologically the area is composed of sedimentary metamorphosed rocks of the Archean system of Precambrian age. The area comes under the Eastern Ghats Mobile belt (EGMB). The strike of the rocks is NNE-SSW. The hill ranges are chiefly grantiferous sillimanite and gneisses (khondalites). These rocks have been intruded by granites, charnockites and dolerites. The area is mostly covered with red and loamy soils together with clay content. The study area is divided into four types of soils-shallow skeletal soils, redloams and clays, gravely loams and clayey soils. As per the 2011 census, the population of the district is 42.88 lakhs with 11.89% of growth rate and this constitutes 5.06% of the population of the state while the geographical area is 11,161 km 2 which is only 4.1% of the total area of the state (source: Handbook of statistics, Visakhapatnam District 2011). As per the 2001 census, the total population of the study area is 237,585 (source: Handbook of statistics Visakhapatnam District, 2011).

Aim and Objective
The delineation of hydrogeomorphological units will help in understanding the composition of the material of the landforms, and identifying more potential groundwater zones which will aid in optimization of the water resources.

Materials and Methods
Remote sening provides indepth information on the morphological structure and their features which are potential ground water zones. Also, satellite data portrays an unbiased picture of the area providing integrated information on different factors controlling the groundwater regime. Realizing the advantages and the potential of remote sensing technology, for deriving hydrogeomorphological information, it was decided to use the latest available satellite data for hydrogeomorphological maps of Meghadrigedda watershed while adopting visual and digital interpretation technique. Existing geological maps and other collateral data were also used, supplemented by field checks with GPS. The entire study has been divided into prefield, field and post field. Survey of India (SOI)

Meghadrigedda Reservoir
The geographic coordinates of the reservoir are East Longitude 83˚11'27" and North Latitude 17˚45'54" respectively. It covers an area of 6.6 sq.km of the study area, a shallow reservoir constructed across the river Meghadrigedda near Kamparupalem village, Visakhapatnam in the year 1972. It is formed at the confluence of two important rivers Meghadrigredda and Naravagedda to supply drinking water to Visakhapatnam city. The gross capacity of the reservoir at FRL is estimated to be 1169 mcft. The dead storage is 1043 mcft. The catchment area is influenced by both southwest and northeast monsoons from June to September, and flash floods occur mostly in October and November due to the influence of cyclones in the Bay of Bengal.

Drainage, Drainage Density and Slope
The drainage demarcation, processing and analysis of the study area has been carried out as a vector layer in ArcGIS 10.0 environment. Stream ordering has been assigned following the rules of Strahler [11] method. Subsequently, morphometric parameters have been computed using standard empirical equations and was carried out in the ArcGIS 10.0. (Figure 2). Drainage density has been discussed and related to many parameters by several Geomorphologists [12] [13] [14] [15] [16].
According to Deju [17] type of "D d " of the region can be categorized as poor,

Hydrogeomorphic Units
Hydrogomorphology mapping using remote sensing data has been conventionally used for delineating ground water prospect zones. In complex terrain comprising fluvial, denudational and structural geomorphic units the intricate relationship among various parameters controlling groundwater regimes is difficult to establish, with GIS tool it is very helpful in analyzing quantifying such multivariate aspects of groundwater occurrence [20] [21].
Hydrogeomorphology operates in an interdisciplinary framework focused on the relationship between hydrologic processes with earth materials and the interaction of geomorphic processes relating surface water/groundwater flow regime [22]- [31]. Scheidegger first defined "hydrogeomorphology" as the study of landforms as caused by the action of water. Dunne [32] describes the early progress in hydrogeomorphology, starting with conceptual geomorphic interpretations evolving to quantitative physically based investigations, and finally to modelling studies.
In geomorphic interpretations, eight fluvial classes were identified out of which four are run-off zones and the rest are infiltration zones. Run-off zones contribute to silt into the plains experiencing siltation of many surface water bodies in the study area.

NDVI and NDWI
These Indices have been used in many applications, including estimation of crop yields and end-of-season above ground dry biomass [33]. NDVI and NDWI for  Table 8, Table 9).

Watershed 3
It is characterized with low slopes, perennial tanks and moderate storage capacity is observed. Prevalence of khondalite rocks and predominant lineaments.
Hdrogeomorphically this watershed is a not good conduit of groundwater as it is covered with pediment. But it has reasonable water source from tanks.

Watershed 4
A very good source of ground water falling into the buried pediplain moderate hydrogeomorphic unit, radial, dendritic and sub-dendritic patterns are observed with prevailing khondalite rock with rolling topography. This watershed is good conduit to ground water.

Watershed 5
It has only few villages under its domain, and is a good source of ground water with prevailing buried pediplain moderate and flood plain.

Watershed 6
A highly conducive unit for groundwater with preponderance of flood plain and buried pediplain moderate. This watershed has main flow of Naravagedda river, a tributary of Meghadrigedda with preponderance of khondalite and quartzite.

Watershed 7
The basin being the drainage for the river Naravagedda is a highly conducive ground water unit hydrogeomorphologically categorized in buried pediplain moderate and flood plain. It has very steep slopes with predominance of rill erosion. Khondalite and migamatite cover the drainage basin. A very giant water source, it has many tributaries draining through the watershed. Home to close to 32 villages, an absolute store house of ground water.

Watershed 8
Adjoining watershed 7, it is located in the upper catchment, not so a good source of ground water with preponderance of buried pediplain shallow consisting of khondalites and Migamites. The overall watershed has a moderate slope with dendritic drainage apart from other different types of drainage.

Watershed 9
This subbasin is the origin of the river meghadrigedda. This unit falls completely under the category of flood plain, but built-up activity has come up tresspassing the flow of water. All the villages are in flood plain with varying types of drainage with prevalence of khondalites. This entire watershed is in floodplain which was once upon a very fertile land for cultivation and huge reserves of water tanks/ponds. Due to the national highway development, there has been a marked increase in linear settlements and conversion of cultivable land to built up land.

Conclusions
Hydrogeomorphology, NDVI and NDWI are strongly interconnected. Drainage, drainage density hydrogeomorphology, groundwater prospects maps have been prepared to show that this entire catchment is highly enriched with ground water prospects (Tables 4-7). NDVI has been prepared to show that a once high vegetative cover is being destroyed which is affecting evapotranspiration and other related issues, which can be seen in all the sub-watersheds. There is a marked decrease in vegetation in all the sub-watersheds from 2010 to 2020.
NDWI has been prepared to show that nature is pouring water, but we are misusing the resource. Good vegetation grows where there is plenty of water and abundance of ground water prevails where there is percolation of water which is seen in flood plain and buried pediplan moderate as good conduits of ground water. With the prevailing population explosion and the catchment dependence on ground water for irrigation and drinking, settlements must not be entertained in the areas that are good percolation tanks for water bodies, tube wells and bore wells. Around the flood plain area of the catchment, in Watershed No. 2 huge agglomerations have come up blocking percolation of water which is giving way to surface run-off and eventually heading to sea, leaving the fields and lands dry, which will in turn affect the vegetation, water for storage in ponds and irrigation as well. Ponds are disappearing as well, which are important containers of reserved water. NDWI for the year 2020 in all the watersheds is displaying plenty of water compared to 2010, which is the result of the thunderous outbursts of the long south-west monsoon that we experienced in 2020. Since the reservoir has reached the dead storage, three flood gates were opened to let off water into the sea. Due to a smaller number of ponds around the catchment, the water could not be stored as well in this latest monsoon of 2020.
There are close to 500 tanks, most of them have silted up, some of the tanks have disappeared as well due to increased construction activity or soil quarrying from the ponds. The tanks must be desilted to increase their storage capacity in the coming monsoon.
The government must take serious measures to curb contracts for housing plots that are destroying arable land which is good for cultivation and water storage, to their profit margin curtailing the nature course and leading to water scarcity. If at all building development is inevitable due to population explosion, Govt must encourage vertical growth of housing in barren areas and save the enriched water storage units.