PERFORMANCE EVALUATION OF GROUNDWATER RECHARGE STRUCTURES: AN APPLICATION OF WATER BALANCE ANALYSIS,

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1 PERFORMANCE EVALUATION OF GROUNDWATER RECHARGE STRUCTURES: AN APPLICATION OF WATER BALANCE ANALYSIS, YOGITA DASHORA, PETER DILLON, BASANT MAHESHWARI, R. C. PUROHIT, HEMANT MITTAL, RAGINI DASHORA, PRAHLAD SONI id:

2 INTRODUCTION Water is a valuable resource and there is a finite supply of it. The growing water scarcity and misuse of freshwater pose serious threats to sustainable development. Rajasthan is the largest state of the country and has scanty rainfall. Due to the above stated reason, 91% of the State s drinking needs and 60% of its irrigation requirements are fulfilled by groundwater. To increase the recharge opportunity, aquifers are artificially recharged in stressed areas. MAR methods include aquifer storage and recovery; aquifer storage, transfer and recovery; infiltration ponds; infiltration galleries; soil aquifer treatment; percolation tanks and check dams (Dillon et al. 2009).

3 STUDY AREA The Dharta watershed of Bhinder block is located between North latitude 24º 37ˊ and 24º 39ˊ, East longitude 74º 9ˊ and 74º 15ˊ E at an altitude 465m above mean sea level and about 65 km from the Udaipur district of Rajasthan (Figure 1(a)). The average annual rainfall is 607mm. The temperatures in the area are in the range between 19º to 48º centigrade during summer and 3º to 28º centigrade during winter. Thickness of the upper soil surface is one meter and underlying formation is Granite gneiss hard rock up to 28m depth (Annon., 2011). The study area is a non- command area where supplemental irrigation (during dry spell in monsoon) in Kharif as well as water requirements in Rabi seasons are fulfilled by groundwater.

4 LOCATION MAP (a) (b) Figure 1 Location of study area and monitoring wells (c) Hinta MAR structure and three monitoring wells (c)

5 STUDY AREA (Contd ) The watershed is situated in an over-exploited block of Udaipur; where groundwater extraction has reached above 100%. The stage of groundwater exceeded the permissible limit and thus, the over exploited aquifer requires augmentation of groundwater for sustaining the abstraction structures (CGWB, 2010) In the Dharta watershed four villages viz. Hinta, Dharta and Sundarpura (inside watershed) and one village Badgaon (outside watershed) were selected. In each village one recharge structure was monitored. The water balance study components were observed at the following structures: Badgaon (B-MAR), Dharta (D-MAR), Hinta (H-MAR), and Sunderpura (S-MAR).

6 METHODOLOGY Selection of Groundwater Recharge Structures Field monitoring Catchment delineation Data Analysis

7 SELECTION OF GROUNDWATER RECHARGE STRUCTURES In this paper, one of the study site results are presented(hinta-mar) with water level changes in MAR structures and nearby wells. The reservoir scale water balance approach was applied to calculate the recharge. The design specifications are: The crest length of Hinta structure is 45.1 m and crest height 2.62m from the stream bed. The ponded area and catchment area of the structure were measured.

8 FIELD MONITORING: (i) Water level in Anicut: Daily basis Monitoring was conducted with the help of people participation. The local community engagement was an important key factor in the data collection framework. Water level gauges were painted for recording stage of water level of recharge structures. Observations were taken for the monsoon season of 2014 and continued while the water remained in the structure. Monitoring was started on 17 th July, 2014; as runoff water harvested in the structures from the first heavy rainfall event. Level surveys were carried out on each anicut for calculating water spread area and area- elevation curves.

9 (ii)rainfall: Daily basis The rainfall data was been recorded on a daily basis using semiautomatic tipping bucket type, ordinary rain gauges and Automatic weather station. The rain gauges were installed around1km distance from structures. Tipping bucket Rain gauge

10 CATCHMENT DELINEATION & DATA ANALYSIS The area contributing water to each structure was delineated using Arc-GIS, Arc- SWAT software. The semi-automated watershed delineation approach was used for catchment delineation. Area-volume calculations The area of ponded water was calculated by making contours from dumpy level/total station survey data. Area of contour was calculated using graph and Planimeter. The volume entrapped between contours were calculated by Trapezoidal Rule and cone formula.

11 WATER BALANCE COMPONENTS In this study, water stored in the check dam is not pumped for irrigation or any other purpose and therefore the alteration in volume was considered due to infiltration and evaporation. The water balance can be written as: (Inflow)- (Losses) = (Change in storage) So Inflow = Rainfall and Runoff Losses= Evaporation and infiltration

12 RESULTS AND DISCUSSIONS Rainfall in the study area is erratic in nature and spatially varied. Village Hinta received a maximum rainfall with 25 rainy days (754 mm), Badgaon 30 days (504 mm), Dharta rainfall 16 days (535mm) and Sunderpura received a minimum rainfall among the four monitoring villages 20 rainy days (484.6mm). One of the recharge structures is shown in Fig at different stages; empty, up to sill level and overflowing in the monsoon season of 2014.

13 RECHARGE AT H_MAR STRUCTURE SCALE AND WATER LEVEL FLUCTUATION

14 Water level fluctuation of the Hinta recharge structure (H_MAR) was measured in 2014 as is shown in above Figure. The water level of H_MAR varies from 0 (empty) to 2.72 m (maximum) with five overflowing events. The surface water balance was calculated i.e. inflow: runoff generated from the catchment, cumulated recharge. It was estimated that cumulative recharge is 63% (recharge about m 3 ) of total inflow. This structure captured 74% runoff of the total amount. Similar results was established by (Parimalarenganayaki & Elango, 2014) in which 63% of cumulative storage was infiltrated as groundwater recharge.

15 Sr. No. Recharge structure Total depth, m ESTIMATION OF WATER BALANCE COMPONENTS OF RECHARGE STRUCTURES 2014 Water Spread area, m 2 Capacity, m 3 Cumulative Recharge, m 3 Cumulative Inflow, m 3 Cumulative Recharge/Cumulative Inflow, % Spill Emptied 1 Badgaon , , ,012 44% Yes Oct-14 2 Dharta , , ,097 34% Yes Dec-14 3 Hinta , , ,969 63% Yes Jan-15 4 Sunderpura ,400 46,935 55,180 85% No Oct-14

16 COMPARISON OF DIFFERENT RECHARGE SITES As illustrated above in Figure the recharge capacity of different structures varies from to cu m. The recharge induced by the Hinta MAR structure is the maximum amongst four structures, with longer duration of storage until mid-january. It also has extra recharge opportunities as compared to other structures. Although these structures are situated in the same watershed the hydraulic loadings varies significantly between structures. The Sunderpura structure captures 100 percent runoff and received hydraulic loadings less than design capacity.

17 INTERACTION BETWEEN SURFACE AND GROUNDWATER The surface water level variations were plotted along with the groundwater column fluctuation of nearby wells. It was found that the distance from the recharge structure has a more pronounced effect on recharge at Hinta MAR Structure. The wells selected for daily monitoring were H13, H14 and H34. Well no. H13 and H14 are situated at the downstream side of the structure and H34 at the upstream side. Distance from H34 to MAR structure is minimum and recharge was higher as compared to the remaining two wells. The variation in groundwater levels in wells and water levels in MAR structures was compared on the basis of time. The wells water levels were also showing similar trends.

18 CONCLUSIONS In this study, water balance approach was used for evaluating the impact of the anicuts as managed aquifer recharge structure. This study exhibits the spatial impact of recharge from anicuts on nearby wells and quantifies the amount of recharge for further improvement in deciding capacity of a structure without obstructing the downstream flow of water. Such studies will help to calculate the potential recharge site of new MAR structures. Further, site specific studies will help in preparing frame work for better management of groundwater recharge.

19 THANK YOU Acknowledgements: This research work was funded by Australian Centre International Agricultural Research (Project name: MARVI; Project No.: LWR/2010/015) through International Water Management Institute (IWMI).