The Groundwater Constraint

Transcription

1 The Groundwater Constraint Responses to Falling Water Tables in India Aaditya Dar 1, Ram Fishman 2 and Meha Jain 3 1 George Washington University, 2 Tel Aviv University & 3 Standford University June 28, 2016

2 Outline Introduction Motivation Research Question Groundwater: levels and trends Responses to groundwater depletion Findings District level analysis Spatial analysis Discussion

3 Motivation Agriculture employs 3 out of 5 people in India Its growth is key to economic development but recent growth has been sluggish Irrigation plays a critical role in agricultural development

4 Figure 1: Coverage of irrigation in India, Source: IndiaStat

5 Motivation Two main sources of irrigation: surface irrigation (tanks, canals) and groundwater irrigation (wells) Groundwater irrigation sustains about 60 percent of India s agriculture and 85 percent of rural domestic water requirements (Sekhri 2011; CGWB 2011) Nearly one in four ground wells have been categorized as unsafe

6 Figure 2: Situation of ground water assessments units in 2004 and 2009 Source: CGWB GOI 2011

7 Context Consider the circumstances leading to the green revolution: India loses some of its most productive agricultural regions during the partition in 1947 Primary focus of planning: industrialization Population increasing; foreign exchange reserves dwindling increasing reliance on US food aid China war in 1962; back-to-back droughts in 1964 and 1965

8 The new agricultural strategy India adopts NAS at cost of exacerbating regional divide (historical trap) Institutional arrangement for canal irrigation was restrictive Subsequent spread of green revolution driven by the unregulated use of groundwater Success achieved at the cost of increasing ecological stress (environmental trap)

9 Research question What is happening to groundwater over time in India? How do farmers respond to depleting water tables?

10 Data Unbalanced panel of over 15,000 wells from 1996 to 2012 Each year, observations are taken at four points of time (68 time periods): Post-monsoon rabi season (typically January) Pre-monsoon season (could be either April, May or June) Monsoon season (typically August) Post-monsoon kharif season (generally November)

11 Table 1: Distribution of wells in major Indian states State N(Wells) N(Districts) N(Tehsils) AP 2, BR CT GJ 1, HR JH KA 1, KL

12 State N(Wells) N(Districts) N(Tehsils) MH 1, MP 1, OR 1, PB RJ 1, TN 1, UP 1, WB 1, Total 17, ,976

13 Figure 3: Monitoring wells in India

14 Figure 4: Groundwater depth, absolute levels

15 Figure 5: Groundwater depth, absolute levels

16 Figure 6: Groundwater depth, absolute levels

17 Empirical strategy Panel estimation, including seasonal fixed effects D t = α + βtimeperiod + γ s + e t where, D t is groundwater depth, TimePeriod is a (year, season) pair and γ s is a dummy for each of the four seasons.

18 Figure 7: Groundwater depth, trends Note: The map plots sign of β in Equation??

19 Figure 8: Groundwater depth, trends Note: The map plots sign of β in Equation??

20 Figure 9: Groundwater depth, trends Note: The map plots sign of β in Equation??

21 Figure 10: Groundwater depth, magnitude of trends Note: The map plots magnitude of β in Equation??

22 Figure 11: Groundwater depth, magnitude of trends Note: The map plots magnitude of β in Equation??

23 Figure 12: Groundwater depth, magnitude of trends Note: The map plots magnitude of β in Equation??

24 Figure 13: Groundwater depth, magnitude of statistically significant trends at district level (including seasonal FE)

25 Figure 14: Groundwater depth, magnitude of statistically significant trends at tehsil level (including seasonal FE)

26 Second question How do farmers respond to falling groundwater, in particular does area under irrigation for major food grains increase or decrease when water table falls?

27 Empirical strategy IrrigatedArea d,t = αdepth d,t +βprepic d,t +γ t +δ d +ɛ d,t (1) Data Land use statistics, Rainfall data, Water table data,

28 Sample Table 2: Distribution of districts in the panel Total Andhra Pradesh Gujarat Haryana Karnataka Madhya Pradesh Punjab Tamil Nadu Uttar Pradesh Total

29 Table 3: Impact on irrigated area (1) Gross (2) Net (3)IV (4)Ground (5)Surface D d,t *** *** * *** (940.57) (720.44) ( ) (714.23) ( ) P d,t 68.11*** 49.11*** 12.78** 26.70*** 15.06*** (12.70) (10.01) (18.96) ( ) (6.52) N R-sq Time FE Yes Yes Yes Yes Yes District FE Yes Yes Yes Yes Yes

30 Figure 15: Correlations between groundwater depth and irrigated area, yearwise

31 Figure 16: Correlations between groundwater depth and irrigated area (from 5 percent sample of wells)

32 Table 4: Impact of change in watertable on irrigated area in 3km radius around well (1) (2) (3) (4) (5) (6) Panel A: November (0.047)*** (0.032)*** (0.033)*** (0.030)*** (0.018)*** (0.013)*** N Panel B: Annual (0.043)*** (0.021)*** (0.021)*** (0.019)*** (0.012)*** (0.010)*** N Well FE No Yes Yes Yes No No Year FE No No Yes Yes No No Interactions No No No State Year District Year Tehsil Year Note: The response variable is irrigated area in a 3km radius of the monitoring well. The main dependent variable is average depth of groundwater in the entire calendar year (measured in meters below ground level). Standard errors are clustered at the tehsil level.

33 Table 5: Impact of change in watertable on irrigated area in 10km radius around well (1) (2) (3) (4) (5) (6) Panel A: November (0.046)*** (0.029)*** (0.029)*** (0.025)*** (0.013)*** (0.007)*** N Panel B: Annual (0.042)*** (0.019)*** (0.019)*** (0.017)*** (0.009)*** (0.006)*** N Well FE No Yes Yes Yes No No Year FE No No Yes Yes No No Interactions No No No State Year District Year Tehsil Year Note: The response variable is irrigated area in a 10km radius of the monitoring well. The main dependent variable is average depth of groundwater in the entire calendar year (measured in meters below ground level). Standard errors are clustered at the tehsil level.

34 Figure 17: Correlations between groundwater depth and irrigated area, statewise (including well fixed effects)

35 Figure 18: Impact of shocks to annual watertable on irrigated area (in 3km radius), statewise

36 Figure 19: Impact of shocks to Jan watertable in various months on irrigated area (in 3km radius), statewise

37 Figure 20: Impact of shocks to Apr watertable in various months on irrigated area (in 3km radius), statewise

38 Figure 21: Impact of shocks to Aug watertable in various months on irrigated area (in 3km radius), statewise

39 Discussion Resolving India s dependence on groundwater Link between electricity subsidy and groundwater extraction Water tables are also falling in other large grain producing nations like China and US