hyperbolic sine of the irrigated area planted in various different crops.

We assign treatment at the district, rather than sub-basin, level. It might seem more natural, given the connected nature of sub-basins, to conduct our analysis at the sub-basin level. But the unit of administration for groundwater management is the district (Bhogale and Khedgikar, 2022). The district is also the unit of treatment for MNREGA and the challenge of assigning MNREGA treatment at the sub-basin level does not have an obvious solution.<sup>16</sup> We discuss the implications of this choice for our estimates at length in Appendix A2 . The primary take-away from this discussion is that if one is concerned about within sub-basin spillovers, our estimates are likely to be a lower bound of the true effect.

# **5 Results & Discussion**

## **5.1 NREGA’s impact on depth to groundwater**

We first present results from the event studies estimated for the depth to groundwater at each point in the year after the implementation of MNREGA. Shown in Figure 2 these event studies suggest that MNREGA led to a substantial reduction in the depth to ground-water across all seasons. We see little to no evidence of pre-trends in the depth to groundwater measured in any of the four seasons.<sup>17</sup> Our difference-in-differences estimates in Table A1 indicate that after the implementation of MNREGA, the depth to groundwater declined by between 7% and 8% after the monsoon seasons and at the beginning of the kharif seasons.<sup>18</sup> We see even larger differences in depth to ground water for measurements taken at the start of the rabi season and prior to the monsoon, of between 11% and 15%. The increase in effect size from the monsoon and kharif seasons to the start of the rabi season may be a consequence of rainfall, that predominantly falls during the monsoon, stored in surface infrastructure having had more time to percolate into the aquifers by the start of the rabi season.

We can also examine the impact of MNREGA implementation using continuous measures for the number of each type of project a given state implemented. In Table A4 we show a continuous measure of the quality of MNREGA implementation - the cumulative total of conservation or irrigation projects completed - that yields similar results to our binary treatment indicator. An additional 100,000 completed conservation projects reduces depth to groundwater by between 4% and 6% depending on the season. Irrigation projects reduce depth to groundwater by a similar 4% to 7%.

> 16These problems are exacerbated by using smaller units of government administration, such as blocks or villages (e.g. Gulzar and Pasquale (2017)).

> 17We also test if districts in different phases of the MNREGA had significant differences in the number of groundwater extraction structures prior to the program. The Fourth Minor Irrigation Census conducted in 2006-07 provides a count of all dug wells and tube wells present in the country. Using these data, we do not detect significant differences in pre-program well characteristics (Table A3).

> 18These results and all of our subsequent difference-in-difference estimates are based on implementing the methodology described in Callaway and Sant’Anna (2021) using their Stata package `csdid` .

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