Wind erosion in groundwater dependent vegetation communities

Background/Question/Methods

Arid and semi-arid vegetation communities are vulnerable to water resource management practices such as groundwater pumping. Groundwater pumping below the root zone of groundwater dependent vegetation (GDV) leads to a decrease in vegetation cover exposing bare soil to wind erosion. Many groundwater dependent areas contain playa lakes that are large sources of global dust emission, and an increase in groundwater pumping below the root zone of GDV in these areas might exacerbate that dust emission. Although research into dust emissions from playas has been extensively studied, there is a lack of research into dust emission in areas of GDV. To enhance our understanding of the mechanisms behind wind erosion in GDV regions, we examined the relationship between chronic groundwater pumping and vegetation cover change and its effects on soil erosion and compared these results to other wind erosion areas. The work was conducted in Owens Valley, California, where a long history of groundwater pumping and surface water diversion has lead to documented vegetation changes.

Results/Conclusions

We examined hydrological and ecological factors across thirteen groundwater dependent alkali meadow sites in Owens Valley. We analyzed vegetation and gap size and installed Big Spring Number Eight (BSNE) catchers to calculate mass transport of aeolian sediment across sites spanning a gradient in vegetation structure and depth to water. The average mass transport across our sites was compared to the mass transport across other sites in the Chihuahuan desert and Minquin County, China. Results across three field seasons show that sediment collected in the BSNE catchers was positively correlated with site gap size. Further, areas that were the most heavily pumped have higher total horizontal flux (Q_tot) than sites that were not pumped. The average Q_tot from our sites is approximately half of the Q_tot produced in the Chihuahuan and Minquin sites. By extrapolating the average Q_tot from our sites over the area of impacted alkali meadow (i.e., due to groundwater pumping) in Owens Valley, the Q_tot is comparable to the Q_tot from Owens Lake. Our results support the hypothesis that loss of vegetation cover due to groundwater decline leaves behind bare soil areas that are easily eroded and might become a significant source of dust emission.