Growing marijuana requires a disconcerting amount of electricity, but finding more efficient ways to power the legal industry isn't the only problem. In California, growers and environmental groups are worried about the impact of large-scale cannabis growing on the state's groundwater supply, especially in times of drought.
According to Mother Jones, "each [marijuana] plant consumes 6 gallons of water a day. At that rate, the plants were siphoning off 180,000 gallons of water per day in each watershed - all together more than 160 Olympic-sized swimming pools over the average 150-day growing cycle for outdoor plants."
Other estimates say that cannabis plants need one gallon of water per day per pound of processed bud - in other words, a one-pound plant needs one gallon of water per day, whereas a five-pound plant needs five gallons per day.
Cannabis cultivation a strain on water resources
It's bad news for a state that a) produces as much as 60 percent of America's marijuana and b) receives, on average, only 15 inches of rain per year. Waterways and reservoirs only provide so much drinking and irrigation water; during dry spells, groundwater provides most of the water supply for farms and cities. In many regions, farmers aren't obligated to recharge any water pumped from the ground.
According to the Nature Conservancy of California, the industry is intensifying drought conditions, as some illegal growers resort to stealing millions of gallons of water, sometimes siphoning away entire waterways to ensure the survival of their crops.
"California Department of Fish and Wildlife biologists found that, in the last five years, Northern California watersheds have seen marijuana acreage under cultivation increase by 55 to 100 percent," they say. "Most marijuana is cultivated outdoors in Northern California, where it increasingly saps already stressed streams and rivers."
A fully legal industry could be more strictly regulated
The answer may well be legal markets that can be more easily regulated. According to organizations like the Nature Conservancy of California, the growers need to conform to stricter regulations - including reserving more substantial funds for enforcement and protection. That cash could, conceivably, come out of tax revenue from a legalization initiative, which the California Attorney General's Office predicts could reap nearly $1-billion in tax benefits.
Further, the Conservancy suggests, "Marijuana growers should be responsible for any environmental damage they inflict, whether they are growing the crop for the black market, the medical market, or, in the future, a potential recreational market."