Borrego Sun - Since 1949

"Mesquite Transects"

 

Last updated 8/7/2019 at 1:28pm



The draft Borrego Basin Groundwater Sustainability Plan claims there are no viable Groundwater Dependent Ecosystems (GDEs) in the Borrego Basin because impacts prior to 2015 have been arbitrarily excluded from consideration; a protocol that is totally unacceptable and defies common sense.

The Borrego Basin has been in overdraft for more than 60 years, so the cumulative adverse impact of the systematic dewatering of the Borrego Valley aquifer on GDEs is excluded by definition.

Mark Jorgensen had a 36-year career with the California State Parks serving as Anza-Borrego Desert State Park Naturalist and State Park Resource Ecologist before being appointed ABDSP Superintendent, a position from which he retired in 2010.

He recently conducted three transects, i.e. a line or narrow area along or within which scientific data is gathered, in Borrego Valley and one in Clark Valley to assess the health of quintessentially groundwater dependent mesquite bosques. The four transects show a profound difference between the health of mesquite in the Clark Valley where virtually no pumping occurs and those dependent on the chronically overdrafted Borrego Valley aquifer.

• Transect #1 done in Clark Valley where 11.8% of the 271 mesquites counted were dead and 88.2% alive.

• Transect #2 done on the south edge of the Borrego Sink where 53.5% of the 981 mesquites counted were dead and 46.5% alive.

• Transect #3 done in eastern Borrego Valley and northern Borrego Sink where 58.9% of 1,763 mesquite trees counted were dead and 41% alive in the area from the Borrego Springs Elementary School eastward to Old Springs Road and the entrance to the Borrego Landfill.

• Transect #4 done at the far eastern terminus of the Borrego Valley Aquifer where 38% of 1,470 mesquite trees counted were dead and 62% alive. This is the low point in the Borrego Sink and the site of the original Borrego Spring marked by the California Historical Landmark known as San Gregorio Monument. Distance from the land surface to water is significantly less here than in other parts of the valley and the transect reflects a higher percentage of live mesquites than the transects done on the south side of the Sink and on the northern edge of the Sink.

Two monitoring wells in the area of this transect show a decline in the water table of 10-13’ in the last decade, so even at this site, far from the nearest extraction well, groundwater decline is significant. The GSP, however, claims that groundwater levels in the area have been “relatively stable.”

In sum, the transect in Clark Valley, where the aquifer has not been mined, resulted in a rate of dead mesquites just over 11%. By contrast, the three transects in Borrego Valley show rates of dead mesquite at 53%, 59%, and 38%. It is clear from these data there are negative impacts of the overdraft in the

Borrego Basin not addressed by the GSP as currently written.

Dennis W. Dickinson

– Florence, Oregon

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