_Table 2: Water Quality Data Sets_

|**Location**|**Mek**<br>**(Cambodia**<br>**an**|**ong River Bas**<br>**, Lao PDR, T**<br>**d Vietnam)**|**in**<br>**hailand,**|**In**|**dia**|**Gl**|**obal (36 cou**|**ntries)**||
|---|---|---|---|---|---|---|---|---|---|
|Source|Mekong Riv|er Basin Com|mission<br>C|entral Water<br>In|Commission f<br>dia|or|GEMStat|||
|Number of Monitoring<br>Stations Included||121||4|25||1,124|||
|Frequency of<br>Observations|Approxim|ately monthl<br>gaps|y, with|Varies b|y station||Varies by sta|tion||
|Years of Observations||2000‐2013||2000|‐2013||2000‐201|3||
|_Table 3: Impact of Electric_<br>Dep Var: Δ log(net primary|_al Conductivit_|_y on Net Prim_|_ary Productiv_|_ity, Mekong R_|_iver Basin_|||||
|productivity)|(1)|(2)|(3)|(4)|(5)|(6)|(7)|(8)|(9)|
|Electrical Conductivity ><br>100 mS/m|-0.0550<br>(0.0138)***|-0.0578<br>(0.0138)***|-0.0605<br>(0.0137)***|-0.0764<br>(0.0149)***|-0.0793<br>(0.0146)***|-0.0834<br>(0.0140)***|-0.0801<br>(0.0163)***|-0.0820<br>(0.0151)***|-0.0851<br>(0.0143)***|
|Precipitation (m/year)|<br>-0.207<br>(0.0282)***|<br>-0.202<br>(0.0236)***|<br>-0.204<br>(0.0226)***|<br>-0.182<br>(0.0352)***|<br>-0.199<br>(0.0293)***|<br>-0.200<br>(0.0282)***|<br>-0.196<br>(0.0469)***|<br>-0.234<br>(0.0404)***|<br>-0.240<br>(0.0387)***|
|Precipitation^2 (m/year)|<br>0.0519<br>(0.00783)***|<br>0.0508<br>(0.00667)***|<br>0.0501<br>(0.00647)***|<br>0.0427<br>(0.00964)***|<br>0.0461<br>(0.00799)***|<br>0.0452<br>(0.00782)***|<br>0.0433<br>(0.0132)**|<br>0.0513<br>(0.0112)***|<br>0.0521<br>(0.0108)***|
|Temperature (C)|<br>0.268|<br>0.223|<br>0.175|<br>0.131|<br>0.109|<br>0.0949|<br>0.117|<br>0.138|<br>0.166|
||(0.0826)**|(0.0628)***|(0.0572)**|(0.116)|(0.0966)|(0.0889)|(0.149)|(0.121)|(0.111)|
|Temperature^2 (C)|-0.00437|-0.00352|-0.00260|-0.00187|-0.00144|-0.00112|-0.00160|-0.00199|-0.00248|
||(0.00153)**|(0.00116)**|(0.00106)*|(0.00213)|(0.00177)|(0.00163)|(0.00271)|(0.00220)|(0.00203)|
|Year Fixed Effects|Y|Y|Y|Y|Y|Y|Y|Y|Y|
|Gridcell Fixed Effects|Y|Y|Y|Y|Y|Y|Y|Y|Y|
|Geographic Time Trends|Country|Country|Country|Country|Country|Country|Country|Country|Country|
|<br>Distance to nearest station|<br>50km|<br>100km|<br>150km|<br>50km|<br>100km|<br>150km|<br>50km|<br>100km|<br>150km|
|Cropland Threshold|>30%|>30%|>30%|>75%|>75%|>75%|>90%|>90%|>90%|
|N|2623|3784|4367|1746|2576|2986|1224|1821|2144|
|R-sq|0.647|0.674|0.689|0.610|0.645|0.657|0.588|0.620|0.630|

Notes: Table shows results from estimating equation 1 for the Mekong River Basin sample via ordinary least squares. Each column is from a separate regression. Specifications across regressions remain constant, with only the sample of gridcells included differing. Columns 1‐3 include gridcells where land area is at least 30 percent cropland. Columns 4‐ 6 restrict the sample to gridcells to those with at least 75 percent cropland, and columns 7‐9 restrict to sample to gridcells with at least 90 percent cropland. Gridcells are also restricted based on the distance to the nearest upstream monitoring station. Columns 1, 4, and 7 include gridcells less than 50km from the nearest upstream station, columns 2, 5, and 8 include gridcells less than 100km from the nearest upstream station, and columns 3, 7, and 9 include gridcells less than 150km from the nearest upstream station. Standard errors clustered at the gridcell level are in parentheses. Stars denote level of statistical significance: + p<0.1, * p<0.05, ** p<0.01, *** p<0.001 19