# Introduction .5% of Earth's water is fresh water out of which 68.9% is of Glaciers and Ice caps, 30.8% is locked up in ground. Only 0.3% is surface water which serves most of life needs [1]. Water is a primary requirement for our daily activities, Safe and readily available water is required for public health, food production, recreational use, drinking and domestic use. Water management is directly relatable to the economic growth of the country, Water availability is one of the primary criteria for setting up of industries which are associated with local and foreign investments. Majorly many parts of North Karnataka are facing water crisis which is also an indirect reason for poor generation of employment opportunities hence many youths are heading towards metropolitan cities like Bengaluru resulted in rapid increase of population failure of typical water supply system to meet the requirement. According to Composite Water Management Index, August 2019 released by NITI Aayog 5 out of 20 world largest cities are under water stress are in India, Indian urban population is expected to reach 600 million by 2030 with expected demand supply gap of 50Bcm [2]. In recent years India has experienced weak monsoons resulted in drought conditions at many places. Ground water table is reducing day by day in many parts of the country, Punjab which produces 10% of India's paddy utilizes 80% ground water for paddy irrigation depleting its own ground water resource, 70% of India's thermal power faces water stress by 2030 which contributes 83% of India's energy power generation in 2016, Presently 40% of India's thermal power plants are in water scare regions, 14 of them faced shutdown in 2013-16 due to water scarcity [2]. Recently Indian government introduced ministry of jalshakthi, which launched programs like Jalshakthi abhiyan to encourage and promote water conservation, Rain water harvesting, renovation and rejuvenation of water bodies, bore well structures. Once a drought village Jakhni of Bunderkhand district, Uttar Pradesh is emerged as self-water reliable village by adopting methods like collection and storage of rain water, Restoration of ponds, Grey water usage with no external funding. Sustainable water management has to be incorporated in private and public buildings to overcome the water demand. Decentralized approach has to be adopted in order to achieve this state. Rain water harvesting by roof top water collection and ground water improvement by simple techniques are the easy, suitable and sustainable solutions for the problems associated with water requirement and its management. # II. Rain Water Harvesting and Ground Water Recharge Rain water is the ultimate and primary source of fresh water. Lakes, ponds, Rivers, Ground water are the secondary sources. Rain water has highest potential to meet the demand of people if public are involved in conservation of rain water in their houses, public building's, Institutions. Rain water harvesting has been carried out from decades from simple harvesting techniques like collection of water through small drums by using normal cloth as a filter medium to modern techniques. Rain water harvesting is defined as collection of rain water from the surface where it falls, either it may be roof top harvesting or open space harvesting. Rain water harvesting potential depends on catchment area, intensity of rainfall. Rain water collected is stored and utilized or the water from open source can be utilized for ground water recharging. Year 2021 ( D D D D ) C Rain water is collected from roof tops and is filtered to remove dry leaves, waste materials, dirt present on the roof top, the water is taken to storage tank which can be overhead tank, surface tank and overhead tank by using down take pipes. The stored water can be treated and can be used as potable water or can be used for non-potable purposes like irrigation, gardening etc. The stored water can also be used for recharging of ground water by different methods such as recharging through establishment of recharge pits or trenches, constructing artificial recharge wells or by using abandoned or existing bore wells. average annual rainfall of 877.8 mm [3]. Satellite view of RVCE campus is shown in figure 1 below. The main motto of the institution to achieve sustainability in terms of water, energy and waste management, in road to achieve this the institution has setup rain water harvesting units in three phases across the campus which has collection capacity of 3.6 lakh liters in total, two bore wells are also established for the purpose of ground water recharging, Campus also has Reverse osmosis water treatment and softening plant of 22000 liters capacity and Sewage treatment plant of 50 kld output [4]. # Objectives Present study aims at estimating potential of rain water and runoff which can be collected annually from different roof top area of different buildings located at RVCE. V. Methodology By harvesting rain water from different buildings of RVCE we can collect 21492572 liters of water annually making RVCE campus self-reliable and self-sustainable in water usage. Collected water can be utilized for flushing, gardening purposes, since the daily requirement of the institution is high adopting RWH techniques is found to be simple and sustainable technique which can be implanted in the campus. # VIII. Estimation of Runoff Potential Runoff is defined as the ratio of precipitation that makes its way towards rivers or oceans as surface or subsurface flow to the precipitation received. After undergoing infiltration and other loses from the rainfall, to determine potential runoff water that can be collected from different catchment surfaces like playgrounds, parks, pavements etc. present at RVCE campus, figure 4 and figure 5 shown below gives satellite image of cricket ground and site respectively. area of the catchment surfaces are determined using Google earth and represented in table 3, runoff coefficients of different surfaces were collected and annual water yield from runoff is obtained by knowing area and average annual rainfall of the catchment. Annual water yield, Q is obtained by using the formula Q = R x A x C Where, R is the average annual precipitation A is the catchment area C is the runoff coefficient Runoff coefficient of pavements = 0.7-0.95, parks = 0.1-0.25, unimproved areas = 0.1-0.3, tiles = 0.8-0.9, playgrounds = 0.2-0.35 [5]. The runoff water which can be collected from different surfaces such as pavements, parks, sites, playgrounds located at RVCE campus is 32725384.29 liters which can be utilized for recharging of ground water by adopting recharge structures. # IX. # Conclusions The present study concludes that by adopting RWH facility to collect the water from roof tops of all the buildings of RVCE campus, 21.49 Million liters of water can be collected. It is evident that adopting RWH and artificial ground water recharge techniques in all the public buildings can be a solution to water availability and management problems at urban areas. 1![Figure 1: Satellite view of R V College of Engineering (Source: Google Earth®) IV.](image-2.png "Figure 1 :") 2![Figure 2: Satellite image of New cauvery hostel (Source: Google Earth®) Annual rain water yield is given by the formula Q = A x R x C x F Where Q = Annual rainwater yield A = Catchment area in m2 R = Annual precipitation C = Runoff coefficient of catchment material Annual rain water yield of Cauvery hostel Catchment area, A = 2632 m2 Annual precipitation, R = 877.8mm Runoff coefficient of RCC roof, C = 0.8 [5] Filter efficiency, considering F = 0.8](image-3.png "Figure 2 :") 3![Figure 3: Satellite image of civil department building (Source: Google Earth®)](image-4.png "Figure 3 :") 45![Figure 4: Satellite image of cricket ground (Source: Google Earth®)](image-5.png "Figure 4 :Figure 5 :") 1. Obtaining roof top area of different buildings atRVCE campus using Google earth.2. Collection of rainfall data from India MeteorolgicalDepartment (IMD) website.3. Runoff co-efficient of different materials are obtainedfrom4. A building is considered and the monthly/annualwater demand and monthly/annual rain water yieldfrom the roof top area is measured and the rainwater harvesting tank capacity is determinedaccording to IS 15979: 2008.5. Similar calculations are extended to other buildings of RVCE to obtain total potential of Rain water. New Cauvery hostel, © 2021 Global Journals 1MonthAverage Rainfall (mm)Monthly yield(l)Cumulative yield(l)Monthly demand(l)Cumulative demand(l)Volume stored(l) Surplus(l)May9616171016171015840015840033103310June85.714435930606915840031680000July100.3168953475022158400475200010553August117.81984316734531584006336003985340031September194.63277991001252158400792000209252169399October154.52602521261504158400950400311104101852November43.973948133545215840011088002266520December15.82661413620661584001267200948660January2.338741365940158400142560000February6.4107801376720158400158400000March16269511403671158400174240000April44.5749591478630158400190080000Total877.814786301900800 1D D D D )(CVII.Annual 2Year 2021Sl. No.Building nameAreaAnnual water yield1Department of CV1535.81862805.772Department of ME1431.69804311.983Department of CSE1063.36597387.144Department of EC1262.1709037.68( D D D D ) C5 6Department of EEE Department of AS and ISE1773.06 1911.81996090.92 1074039.567Department of BT and EIE1050.23590010.818Department of MCA1596.28896777.339Department of TE894.95502775.7510CRC Complex803.41451349.3111Department of CE1586.42891238.0612Administrative block1330.78747621.5513Mechanical PG block486.43273272.4814Department of IEM925.75520078.9415Old sports complex547.44345990.8316New sports complex & Gym center1239.1826638.3017Food Court1354.09855806.5418Bank and Post office153.2986117.0919Aero-space lab862.21575204.4320Library building873.11490506.2121Hospital Building301.61169442.0822Cognitive and Research Block863.28484983.7823Workshops3213.012143488.93524Old cauvery hostel1251.64703161.3325New cauvery hostel26321478636.5426Sir m v hostel2041.951147151.1727Chamundi hostel1159.33651302.31 3Sl. No.Type of catchmentArea (m 2 )Annual water yield(l)1Pavements27913.0611760975.12Play grounds20507.544950417.623Unimproved areas/ sites37633.288258623.34Parks/greenery24187.234246310.15Brick/tiles/concrete4996.953509058.17Total runoff32725384.29 1D D D D ) C( D D D D )(X.C 2. © 2021 Global Journals © 2021 Global Journals * Website of NASA earth observatory * by NITI aayog in association with Ministry of Jal Shakti and Ministry of Rural Development august 2019 Composite water management index * Ministry of Earth Sciences Government of India Indian Meteorological Department * Rain water harvesting in India, 2007 an appraisal by Central pollution control board, Ministry of Environment, Forests and Climate change Government of India * IS 15797: 2008 Roof top Rainwater harvesting -Guidelines, BIS New Delhi, India