Impacts of Surface Water Diversions for Marijuana Cultivation on Aquatic Habitat in Four Northwestern California Watersheds

Abstract

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.

A global approach to estimate irrigated areas – a comparison between different data and statistics

“…The example of California shows that the available statistics differ remarkably, which leads to strong impacts on the validation results. The water rights complaints in California regarding "Unauthorized Diversion" prove the existence of illegal irrigation activities (California Environmental Protection Agency, 2017), which are not part of the official statistics and are not only an issue of smallholder farmers or of watering lawns (Bauer et al, 2015). The comparison of our irrigation map with a study of irrigated areas in India shows a smaller relative error compared to the irrigation map of the USA.…”

Full Issue PDF, Volume 41, Issue 6

“…In addition to these effects from urbanization, as human populations grow and their demands for water also grow, there may be less water to support Pacific trout (Vörösmarty et al 2000). The rise of the illegal drug trade in remote areas of western North America in recent decades is also likely having a negative effect on native Pacific trout, through water withdrawals (Bauer et al 2015) and the use of agricultural chemicals, but the specific effects are difficult to document. The likelihood of extreme water scarcity has been brought into direct focus in the wake of an exceptional regional drought that gripped much of the Pacific Region of western North America in recent years (Wise 2016 …”

“…Wide light bars depict continued effects following the initial period of rapid change. Concurrent change in human population size for the Pacific Northwest of the United States is shown, but we added climate change (IPCC 2013), invasive species and domestication(Sanderson et al 2009), and illegal drug activities(Bauer et al 2015).Downloaded by [University of California Santa Barbara] at 16:41 22 June 2016…”

Opportunities and challenges of interbasin water transfers: a literature review with bibliometric analysis

“…Semiarid and arid regions occupy one-third of the world's land surface area (Thomas 1989;Comín and Williams 1994;Walker et al 1995;Kingsford et al 1998). Reviewed research suggests that water resource scarcity and habitat degradation in TP total publications, FCA publications as first author or corresponding author, TC total citations, CPP citations per publication, R rank in the list, CAS Chinese Academy of Sciences most of the world is likely to worsen in the future (Bauer et al 2015;Li et al 2015;Liu and Ma 1983;Loáiciga et al 2000). Water transfer/diversion projects were commonly implemented to mitigate water resource deficits in drought-stricken regions.…”