Step Two: Become renewable water self-sufficient

Become renewable water self-sufficient. Water is essential to life. It is essential to the water-rich lifestyle most people in the developed world already have and that people in the developing world would like to have. The population of the Greater Tijuana part of the region is more or less the same as the population of San Diego County, currently, 3,100,000 people. If this is true, the San Diego/Tijuana Region has a population of 6,200,000.9 + Also assumed is that everyone in the Tijuana part of the region would like to use the same amount of water per capita as is used per capita in San Diego County, around 180 gallons per capita per day. + Given the assumptions above and assuming the worst case scenario of zero rainfall, zero recycled wastewater and zero imported water, can the San Diego/Tijuana Region become freshwater self-sufficient using renewably generated electricity to convert seawater into freshwater through reverse osmosis (RO)? The answer is a resounding yes. Installing commercially available 20% efficient PV panels over 4% of the roofs and parking lots on either side of the San Diego/Tijuana Region, will produce 11,519,600 kWh of electricity per day or 23,039,200 kWh per day if the electricity produced on both sides of the border is added together.

Generating 23,039,200 kWh per day times 365 days per year equals 8,409,308,000 kWh per year. Multiplying 8,409,308,000 kWh per year times 65 gallons of freshwater per kWh of electricity consumed, equals 546,605,020,000 gallons of freshwater per year. Dividing 546,605,020,000 gallons by 7.48 gallons per cu, ft. equals 73,075,537,430 cu. ft. of water. Dividing 73,075,537,430 cu. ft. of water by 43,560 cu. ft. per acre foot equals 1,677,583 acre feet of water each year or 838,792 acre ft. of freshwater on each side of the border. (One acre ft. = 4,034 cu. meters.) For reference, the San Diego County side of the region currently uses around 610,000 acre ft. of fresh water per year including county based agriculture. If the region used cost-effective and life-support-system-effective ways to use water more efficiently, (low water use toilets, using graywater and disinfected recycled sewage water for irrigation, drip irrigation, collecting and storing rainwater runoff, etc.), only 1.5% of the roofs and parking lots in the region would need to be covered with 20% efficient PV panels to make the whole region completely renewable water self-sufficient.

To protect sea life from the RO process, sand filtered seawater will be extracted from wells close to the ocean. This way, eggs and small fish will be kept out of the RO process. Since the wastewater from the RO process will be twice as salty as seawater, it will be evaporated in shallow open ponds so salt and other minerals left behind can be mined. If any RO waste water needs to be returned to the ocean, it would be diluted by sand-filtered seawater to be no more than 20% saltier than natural seawater before being released into the ocean, diffusely. -To protect sea life from the RO process, sand filtered seawater will be extracted from wells close to the ocean. This way, eggs and small fish will be kept out of the RO process. Since the wastewater from the RO process will be twice as salty as seawater, it will be evaporated in shallow open ponds so salt and other minerals left behind can be mined. If any RO waste water needs to be returned to the ocean, it would be diluted by sand-filtered seawater to be no more than 20% saltier than natural seawater before being released into the ocean, diffusely.

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