reported electricity generation to estimate water consumed for each power plant. Key assumptions about what cooling technologies were used for each individual power plant were compiled from the Union of Concerned Scientists’ [12] power generation database. The water intensity (gallons per MWh) of different types of power generation and cooling technologies were compiled from Mielke [9] and et al. updated with operational values from Macknick [26]. For each power plant, the average water et al. intensity was multiplied by the monthly power generation to obtain water consumption estimates (see Supporting Information for more the known ranges of water intensity). Coal and natural gas used in Pennsylvania production It is impossible to track the path of every molecule of natural gas or every tonne of coal from extraction to consumption in power production. As a result, the end product results were calculated under the assumption that the proportion of fuel consumed in the power sector applies uniformly across watersheds. The amount of fuel extracted for use in power generation was estimated using EIA datasets (Tables S3 and S4). Table S3. Coal extraction and coal used for power generation in Pennsylvania [27, 28]. Year Coal consumed for power Coal extracted Proportion coal generation (Thousand Short (Thousand short produced consumed in tons) tons) power 41,602 55,506 0.75 2012 2011 47,403 59,899 0.79 2010 50,888 58,964 0.86 2009 48,853 59,143 0.83 Table S4. Shale gas extraction and use in power generation [29, 30]. Year Pennsylvania Natural Pennsylvania Natural Pennsylvania Proportion Gas Deliveries to Gas Gross market gas of gas Electric Power Withdrawals from production delivered Consumers Million Shale Gas Million (MMcf) to power Cubic Feet Cubic Feet consumers 2012 393775 2042632 2256696 0.17 2011 306266 1068288 1310592 0.23
reported electricity generation to estimate water consumed for each power plant. Key assumptions about what cooling technologies were used for each individual power plant were compiled from the Union of Concerned Scientists’ [12] power generation database. The water intensity (gallons per MWh) of different types of power generation and cooling technologies were compiled from Mielke et al. [9] and updated with operational values from Macknick et al. [26]. For each power plant, the average water intensity was multiplied by the monthly power generation to obtain water consumption estimates (see Supporting Information for more the known ranges of water intensity). Coal and natural gas used in Pennsylvania production It is impossible to track the path of every molecule of natural gas or every tonne of coal from extraction to consumption in power production. As a result, the end product results were calculated under the assumption that the proportion of fuel consumed in the power sector applies uniformly across watersheds. The amount of fuel extracted for use in power generation was estimated using EIA datasets (Tables S3 and S4). Table S3. Coal extraction and coal used for power generation in Pennsylvania [27, 28]. Year Coal consumed for power generation (Thousand Short tons) Coal extracted (Thousand short tons) Proportion coal produced consumed in power 2012 41,602 55,506 0.75 2011 47,403 59,899 0.79 2010 50,888 58,964 0.86 2009 48,853 59,143 0.83 Table S4. Shale gas extraction and use in power generation [29, 30]. Year Pennsylvania Natural Gas Deliveries to Electric Power Consumers Million Cubic Feet Pennsylvania Natural Gas Gross Withdrawals from Shale Gas Million Cubic Feet Pennsylvania market gas production (MMcf) Proportion of gas delivered to power consumers 2012 393775 2042632 2256696 0.17 2011 306266 1068288 1310592 0.23
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