EFFECTS OF IRRIGATION WITHDRAWAL AND CLIMATE CHANGE ON GROUNDWATER DYNAMICS IN A SEMI-ARID INDIAN WATERSHED Rajendra Sishodia Sanjay Shukla, UF Suhas Wani, ICRISAT Jim Jones, UF Wendy Graham, UF
GROUNDWATER USE IN INDIA Groundwater accounts for 70% of water used for irrigation (Siebert et al., 2010) 50% of total crop production comes through groundwater irrigation Groundwater use increasing since 1960 Highest user of groundwater in the world - 240 bcm/year (Shah, 2009) Figure 1 Groundwater use in different countries (Shah, 2009)
FACTORS AFFECTING INCREASED GROUNDWATER USE Seasonal/unreliable surface water resources Resilient buffer against natural climatic variability - On demand availability Fast installation and low installation cost Free/subsidized electricity
GROUNDWATER DEPLETION IN INDIA India is largest user of nonrenewable groundwater (Wada et al., 2012) 29% of total groundwater management units in semicritical, critical or overexploited category (CGWB, 2006) GRACE satellite study - 1 feet water table drop/yr in semi-arid NW states (Rodell et al., 2009) Irrigation withdrawals are causing the depletion Would in turn affect the agriculture production due to decreased groundwater availability Limited supply in semi-arid regions Source: CGWB, 2006
HISTORICAL CLIMATE CHANGE Climate change may increase the future GW use and decrease the recharge Atmospheric temperatures have increased by 1 C during last century (Dash et al., 2007) Rainfall patterns are changing in both monsoon and other seasons Number of extreme rainfall events are increasing and moderate rainfall events are decreasing in the monsoon season (Goswami et al., 2006) Monthly rainfall distribution is also changing (Guhathakurta and Rajeevan, 2008) From http://www.mapsofindia.com/maps/india From http://www.mapsofindia.com/maps/india
CLIMATE CHANGE PROJECTIONS FOR INDIA Decrease in number of rainy days along with increase in intense rainfall events (GOI, 2004) More variable monsoon onset/arrival and decrease in winter rainfall leading to droughts during dry and hot summer (Lal et al., 2001) Temporal shifts in rainfall may change the groundwater recharge and availability during different times in the year Climate change may further increase the groundwater demand and reduce the supply by decreasing recharge Increased frequency of high intensity rainfall may increase the runoff and reduce the recharge
GROUNDWATER MANAGEMENT STUDIES Limited studies to quantify the effects of current and future groundwater withdrawals and climate change and to develop and evaluate different crop and water management scenarios Most of the groundwater studies related to saltwater intrusion Most groundwater studies conducted in tropical and sub-tropical humid regions of India groundwater availability is usually higher in tropical and sub-tropical regions due to high rainfall and recharge Rejani et al. (2008,2009) Orissa state Sub-tropical wet Thampi and Raneesh (2011) Kerala state- Humid tropical
HYDROLOGIC MODELS Modeling can be used to determine the effects of current and future groundwater withdrawals and climate change and also to develop suitable crop and water management scenarios MIKE SHE (DHI, 2007), SWAT (Neitsch et al., 2009), VIC (Liang et al., 1994) and MODFLOW (Harbaugh et al., 2000) MIKE SHE and SWAT are the most widely used models climate change, land management, surface water and groundwater management MIKE SHE is a distributed, physically based hydrologic model which can be used to model overland and groundwater flow along with other main hydrologic cycle components DHI
MIKE SHE AND SWAT MIKE SHE - Used extensively to simulate surface and groundwater flows for variety of purposes Climate change - Sultana and Coulibaly (2011) Groundwater management- Demetriou and Punthakey (1999) Irrigation Management - Singh et al. (1998) SWAT is a conceptual, continuous time, semidistributed model developed by USDA to predict the impact of land management on runoff and water quality in large agricultural dominated basins Climate change - Ficklin et al. (2009) Watershed management - Garg et al. (2011)
MIKE SHE VERSUS SWAT MIKE SHE Distributed finite difference cell based model Can simulate cell based spatial and temporal soil moisture and water table fluctuations in multi aquifer system (water availability and soil moisture in individual well fields or famers fields) Simulates groundwater withdrawals from multi-aquifer system Simulates water table fluctuation into and below the soil layer Better simulation of ET from groundwater ET from groundwater is accounted in soil moisture balance Spatio-temporal simulation of moisture and water table helps in designing management scenarios SWAT Lumped HRU based model Only simulates temporal changes in each (shallow and deep) aquifer storage at sub-basin scale and soil moisture at HRU scale Groundwater withdrawals from either shallow or the deep aquifer Assumes aquifer is always below the soil zone- Simplified ET calculation from groundwater ET from groundwater is not accounted in soil moisture balance Does not simulates the water table
OBJECTIVES 1. Use MIKE SHE in conjunction with measured soil-weather-crop-hydrologic data to quantify net groundwater recharge under current and future groundwater withdrawals for an agricultural watershed in semi-arid region of India. 2. Simulate the effects of future climate scenarios, developed from two GCMs, on groundwater levels and surface flows 3. Develop and evaluate appropriate crop and water management scenarios to maintain or enhance the groundwater recharge under current and future irrigation withdrawals and climate change
STUDY SITE http://www.mapsofindia.com/ maps/india/geological.htm From K. Garg, ICRISAT
WATERSHED CHARACTERISTICS Semi-arid Rainfall = 850 mm 85% during monsoon (June-October) Soil Vertisols (black soils) Depth 10-200 cm Topography Average slope <2% Crops Dominent - cotton (July-December) Others - vegetables, sorghum, pigeon pea, chickpea and paddy
WATERSHED GEOLOGY Groundwater Hard rock aquifer Sole source of irrigation Deep and shallow wells Lithology data for Shankarpalli and surrounding Mandals were collected from State Groundwater Board Lithology data, visual analysis of open well profiles and discussion with farmers, NGRI, and GW board geologists suggested that Kothapalli lies in the transition zone of Deccan Traps and Granitic terrain Surficial Aquifer (Weathered Basalt) - 10-13 m Confining Layer (Hard/Massive Basalt) 10-12 m Deeper Aquifer (Fractured Granite) 50-60 m Surface soil (0-2 m)
WATERSHED DATA Weather Kothapalli weather station (1999-continued) Rainfall, temperature, humidity, wind and solar radiation ICRISAT weather data Crops and land use LAI and root distribution (literature) Land use Farmers survey (1999-2012) Soil and geology Moisture retention curves from soil samples Well log data from CGWB and state GW agencies Topography and stream network Total station survey by ICRISAT Existing stream network information and field measurements
HYDROLOGY DATA ICRISAT data on streamflow and monthly shallow well levels from 1999 Soil moisture data (weekly) Capacitance probe Multiple depths Irrigation withdrawals Pressure transducers Flow meter Deep and shallow groundwater levels data Pressure transducers Every 30 minutes Daily manual deep and shallow groundwater levels since July 2011 Underway
Type of well Tube well 16 Tube well 8 Tube well 9 Tube well 11 Tube well 10 Tube well 7 Tube well 9 Tube well 19 Tube well 9 Tube well 12 Tube well 13 Tube well 6 Tube well 17 Tube well 13 Tube well 27 Open well 23 Open well 29 Open well 36 Open well 23 Open well 27 Open well 27 Flow Rate (m3/hr) PUMP FLOW RATES
Open wells water levels in May 2011 613 607 602.75 606 612.25 608 601.5599 598.5 612.75 610612.25 609.25 611.5 606.25 610 609 612 613.5 604 605.25 605.5 605.25 605.25 601.25 602.75 601 598.5 598.75 601.5 597.25 596 596.5 610 Open wells water level in November 2011 618.75 615615 616.25 617.75 616 614.5 616.75 611 608 609 609 613.25609.25608 613 615.25 615.5 613.5 611.25 604.5 604.75 605 606.5 606.75 602605 605 603 603 605.75 608.75 605.25 602.5 602.5 601 600.25 600
Depth of water below surface (m) Rainfall (mm) Shallow Well data for Kothapalli watershed Date 24-07-1998 06-12-1999 19-04-2001 01-09-2002 14-01-2004 28-05-2005 10-10-2006 22-02-2008 06-07-2009 0.0 350.0 2.0 Well ID 1 Well ID 2 Rainfall (mm) 300.0 4.0 250.0 6.0 200.0 8.0 150.0 10.0 100.0 12.0 50.0 14.0 0.0
Depth of water above the sensor (m) Depth of water BGL (m) 5-31-12 6-20-12 7-10-12 7-30-12 8-19-12 9-8-12 9-28-12 6 7 8 9 10 11 12 13 14 15 16 Date 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 31-05-2012 20-06-2012 10-07-2012 30-07-2012 19-08-2012 08-09-2012 28-09-2012 Date Groundwater level fluctuations In deep well (upper left) and open well (lower right)
MODEL CALIBRATION AND VALIDATION Most sensitive and uncertain model parameters would be calibrated Saturated hydraulic conductivity of UZ layers Surface roughness coefficient and detention storage Hydraulic conductivity and specific yield of SZ layers ET parameters in the model C1, C2, C3 Calibration Deep and open wells continuous groundwater level data (June 2012- May 2013) Runoff and monthly open wells groundwater level data for 1999-2007 Daily GW level data from deep and open wells (July 2011-June 2012) Soil moisture data (June 2012-May 2013) Validation Deep and open wells continuous groundwater level data for Monsoon season, June 2013-Dec 2013 Runoff and monthly open wells groundwater level data for 2008-2013 Daily GW level data from deep and open wells (July 2012-Dec-2013) Soil moisture data (June 2013-Dec 2013)
GROUNDWATER USE AND CLIMATE CHANGE SCENARIOS 16 GCMs simulated and downscaled AgMIP scenarios for 2010-2030 and 2040-2070 period (A2 and B1 emission scenario or RCPs) Future groundwater use Historical trend in number of wells, relevant literature and experts opinion Crop and water management scenarios would be developed based on the results of climate change and future groundwater use scenario results Saturated and unsaturated zone fluxes and groundwater levels under different scenarios would be analyzed for monthly/seasonal and annual changes in groundwater recharge and availability
CROP AND WATER MANAGEMENT SCENARIOS Development of appropriate management scenarios according to the quantitative effects on groundwater recharge and levels Crop management Change in planting date Switch to less water consuming crops Irrigation Management Deficit irrigation (whole season or during certain stages) Switch to more efficient irrigation (e.g. from flood - efficiency 40%,to drip- efficiency 90%) Model simulated outputs such as saturated and unsaturated zone fluxes, would be analyzed to quantify the effects of these scenarios on groundwater recharge and levels
GROUNDWATER SURVEY AND DEVELOPMENT AGENCY (GSDA) REPORT In some districts from Western Maharashtra, where groundwater level increased after the implementation of water conservation schemes like check dams, percolation tanks among others. With increased groundwater level, farmers shifted to cash crops like sugarcane, grapes and pomegranate farmswhere water requirement was higher. Within couple of years, the groundwater level went down more than it was earlier because of the excess withdrawal of water. Suresh Khandale, Additional director, GSDA