Voglio sapere a riguardo di…

jbell on DSKJLSW7X2PROD with PROPOSALS

Federal Register / Vol. 86, No. 41 / Thursday, March 4, 2021 / Proposed Rules exacerbated by climate change.
Groundwater pumping or withdrawal leads to aquifer depletion and no or reduced outflow from springheads.
Modification of springheads reduces or eliminates springflow. Water diverted from springheads reduces or eliminates the amount of water supporting the cienega. Drought and warming also reduce springflow and the amount of water in cienegas. Reduction in winter rain particularly leads to reduced aquifer recharge. Climate change is expected to exacerbate drought conditions, increase surface temperatures and evapotranspiration, and reduce winter precipitation, all of which may lead to a reduction in aquifer recharge and increased cienega drying.
Water loss in cienegas reduces the quantity and quality of habitat for the Arizona eryngo. The species requires very moist to saturated soils and possibly some standing water for seed germination. As water is lost from cienegas, soils become drier, reducing habitat quality and allowing woody and/or invasive vegetation to establish, further reducing available habitat.
Water loss from cienegas caused the extirpation of the species at two of the six cienegas known to historically support the Arizona eryngo Las Playas in New Mexico, and Agua Caliente in Arizona, and all populations continue to be exposed to water loss. The sources of water loss are discussed further below.
Groundwater withdrawalThe population at Las Playas was extirpated primarily due to groundwater pumping for agriculture and the Playas Smelter that caused the desiccation of the spring Sivinski 2018, p. 27; Stromberg et al.
2019, p. 5. Groundwater withdrawal is also occurring near Lewis Springs, La Cebadilla, and Agua Caliente. The use of groundwater for agriculture, industry, and urban and rural development has enabled significant human population growth in the arid Southwest. Increased groundwater withdrawal can reduce or eliminate springflow, thereby eliminating wetlands altogether Johnson et al. 2016, p. 52.
The largest municipalities in the Sierra Vista subwatershed, within which Lewis Springs occurs, are Sierra Vista, Bisbee, Tombstone, and Huachuca City. Within these areas, the human population is increasing, as is development distributed in rural parts of the subwatershed Leake et al. 2008, p. 1. This growing population is dependent on groundwater to meet its water consumption needs. Water outflow from the subwatershed, including water withdrawn by
VerDate Sep<11>2014

18:38 Mar 03, 2021

Jkt 253001

pumping, exceeds natural inflow to the regional aquifer within the subwatershed Leake et al. 2008, p. 2.
As a result, groundwater levels in parts of the subwatershed are declining, and groundwater storage is being depleted i.e., a negative water budget.
Groundwater pumping in the area of Lewis Springs, up to several kilometers away, may be affecting the regional groundwater flow to the wetlands along the San Pedro River, including Lewis Springs Stromberg et al. 2019, p. 9.
The continued decline of groundwater levels upgradient from perennial river reaches will eventually diminish the base flow of the San Pedro River and impact the riparian ecosystem within the SPRNCA Leake et al. 2008, p. 2.
This groundwater use over the past century has been so profound that the effects of pumping over the past century will eventually capture and eliminate surface flow from the river, even if all groundwater pumping were to stop Gungle et al. 2016, p. 29. Models show the area of Lewis Springs as being one of the areas of greatest groundwater loss in the basin Leake et al. 2008, p. 14.
The aquifer supporting the La Cebadilla springs could be reduced from numerous private wells including the Tanque Verde Guest Ranch producing water from the aquifer that feeds the springs Eastoe and Fonseca 2019, pers.
comm.. It is unknown how quickly pumping a mile or two away from the springs might affect the springs themselves Eastoe and Fonseca 2019, pers. comm..
We do not have information on the source of water supplying the springs or about the amount of groundwater use at Rancho Agua Caliente or Ojo Vareleno, both in Mexico.
Spring modificationThe Arizona eryngo population at Agua Caliente was extirpated due to a number of manipulations, including spring modification i.e., the springs were blasted in the 1930s and again in the 1960s that significantly decreased the water flow Stromberg et al. 2019, p. 5;
Friends of Agua Caliente 2020, entire and pond impoundment.
Water diversionThe Arizona eryngo population at La Cebadilla has been exposed to water diversion for many decades; this diversion may have led to a reduction in the size of the cienega, but enough water still flows to maintain the cienega and support the largest documented population Fonseca 2019, p. 2; Stromberg et al. 2019, p. 5. Pond impoundment diverts water from the cienega at Agua Caliente; this was pronounced in the 1960s during subdivision construction and has continued since.

PO 00000

Frm 00022

Fmt 4702

Sfmt 4702

12571

Less is known about water loss associated with the cienegas supporting the Arizona eryngo in Mexico, but we are aware that the municipality of Casas Grandes is interested in installing a pipeline from the spring at El Ojo Vareleno to supply water to the Universidad Tecnologica de Casas Grandes. Currently at Ojo Vareleno, springflow is collected in concrete spa ponds, which likely affects the natural hydrology of the site.
Drought and warmingAll Arizona eryngo populations are exposed to drought, as well as warming temperatures from climate change.
Decreased precipitation and increased temperatures due to climate change will exacerbate declines in surface and groundwater levels, which will cause further drying of cienega habitat required by the Arizona eryngo.
Climate change has already begun, and continued greenhouse gas emissions at or above current rates will cause further warming. Climate models indicate that the transition to a more arid climate is already underway and predict that in this century the arid regions of the southwestern United States will become drier i.e., decreased precipitation and warmer i.e., increased surface temperatures, and have fewer frost days, decreased snow pack, increased frequency of extreme weather events heat waves, droughts, and floods, declines in river flow and soil moisture, and greater water demand by plants, animals, and humans Archer and Predick 2008, p. 23; Garfin et al.
2013, pp. 56. Increasing dryness in the southwestern United States and northern Mexico is predicted to occur as early as 20212040 Seager et al. 2007, p. 1181. Climate modeling of the southwestern United States shows consistent projections of drying, primarily due to a decrease in winter precipitation Collins et al. 2013, p.
1080. For both Pima and Cochise Counties, where the La Cebadilla and Lewis Springs populations occur, the average daily maximum temperature, under both lower i.e. RCP 4.5 and higher i.e., RCP 8.5 emissions scenarios, will increase by mid-century Climate Explorer 2020.
Climate change over the 21st century is projected to reduce renewable surface water and groundwater resources in most dry subtropical regions IPCC
2014, p. 69. Over the next 100 years, groundwater recharge in the San Pedro basin is expected to decrease 17 to 30
percent, depending on the climate scenario considered Serrat-Capdevila et al. 2007, p. 63, and average annual base flow will be half the base flow in 2000.
As the area gets drier, the San Pedro
E:FRFM04MRP1.SGM

04MRP1