Monday, March 30, 2015

Unregulated marijuana growing in California is exacerbating drought conditions and endangering aquatic species including federally listed salmon and steelhead trout per peer reviewed study-UK Independent

3/30/15, "California is in one of its worst-ever droughts because people are growing too much weed," Independent UK, Ben Tufft

"The current drought in California, one of the most severe on record, could have been exacerbated by marijuana cultivation, scientists say.

Some marijuana farms are sucking more water from the ground than can be replaced, threatening the state’s water entire supply, according to a study published in the Public Library of Science journal.

The amount of water being used to cultivate marijuana was said to be “unsustainable” in the report.

Smaller streams were found to be completely “dewatered” by the demands of marijuana farming, while larger streams experienced substantial “flow diversions and increased temperatures”.

In some areas the water use was so extensive, fish and other aquatic wildlife were threatened.

The study warned: “Continued diversions at a rate necessary to support the current scale of marijuana cultivation in northern California could be catastrophic for aquatic species.”

Marijuana is illegal to use recreationally in California, but the cultivation of marijuana in California has increased rapidly since 1996, when the use and growth of medical marijuana was legalised.

Marijuana is considered particularly water intensive compared to other crops. Wine grapes, for example, require roughly half as much water as marijuana plants.

California consistently outranks all other states for the number of marijuana plants that are eradicated by law enforcement.

The main areas of cultivation are on private property, located in the northwest of the state, primarily because it is “remote, forested, and sparsely populated”.

Therefore, it is often difficult for authorities and scientists to accurately gauge the extent and the impact of the farming.

The state authorities do not regulate marijuana farms and it had been seen as unrealistic to expect that growers would register for permits to divert water.

But that is now changing following concern over the effect on the environment.

The California Water Resources Control Board is developing a permit that growers in 10 northern counties will be required to obtain.

And water diversion permit checks are being stepped up, with fines starting at $8,000 for each transgression."


"In the most impacted study watersheds, diminished streamflow is likely to have lethal or sub-lethal effects on state-and federally-listed salmon and steelhead trout and to cause further decline of sensitive amphibian species."

3/18/15, "Impacts of Surface Water Diversions for Marijuana Cultivation on Aquatic Habitat in Four Northwestern California Watersheds,"


"Marijuana (Cannabis sativa L.) cultivation has proliferated in northwestern California since at least the mid-1990s. The environmental impacts associated with marijuana cultivation appear substantial, yet have been difficult to quantify, in part because cultivation is clandestine and often occurs on private property. To evaluate the impacts of water diversions at a watershed scale, we interpreted high-resolution aerial imagery to estimate the number of marijuana plants being cultivated in four watersheds in northwestern California, USA. Low-altitude aircraft flights and search warrants executed with law enforcement at cultivation sites in the region helped to validate assumptions used in aerial imagery interpretation. We estimated the water demand of marijuana irrigation and the potential effects water diversions could have on stream flow in the study watersheds. Our results indicate that water demand for marijuana cultivation has the potential to divert substantial portions of streamflow in the study watersheds, with an estimated flow reduction of up to 23% of the annual seven-day low flow in the least impacted of the study watersheds. Estimates from the other study watersheds indicate that water demand for marijuana cultivation exceeds streamflow during the low-flow period. In the most impacted study watersheds, diminished streamflow is likely to have lethal or sub-lethal effects on state-and federally-listed salmon and steelhead trout and to cause further decline of sensitive amphibian species."


parag. 6, "In northern California, unregulated marijuana cultivation often occurs in close proximity to habitat for sensitive aquatic species. Because of this proximity and the water demands associated with cultivation, we chose to focus on the cumulative impacts of low-volume surface water diversions associated with marijuana cultivation. We evaluate these water demands at a watershed scale to determine whether they could have substantial effects on streamflow during the summer low-flow period. In addition, we discuss which sensitive aquatic species are most likely to be impacted by stream diversions and describe the nature of these impacts."...

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