Semi‐Arid Aquifer Responses to Forest Restoration Treatments and Climate Change

Abstract

The purpose of this study was to develop an interpretive groundwater-flow model to assess the impacts that planned forest restoration treatments and anticipated climate change will have on large regional, deep (>400 m), semi-arid aquifers. Simulations were conducted to examine how tree basal area reductions impact groundwater recharge from historic conditions to 2099. Novel spatial analyses were conducted to determine areas and rates of potential increases in groundwater recharge. Changes in recharge were applied to the model by identifying zones of basal area reduction from planned forest restoration treatments and applying recharge-change factors to these zones. Over a 10-year period of forest restoration treatment, a 2.8% increase in recharge to one adjacent groundwater basin (the Verde Valley sub-basin) was estimated, compared to conditions that existed from 2000 to 2005. However, this increase in recharge was assumed to quickly decline after treatment due to regrowth of vegetation and forest underbrush and their associated increased evapotranspiration. Furthermore, simulated increases in groundwater recharge were masked by decreases in water levels, stream baseflow, and groundwater storage resulting from surface water diversions and groundwater pumping. These results indicate that there is an imbalance between water supply and demand in this regional, semi-arid aquifer. Current water management practices may not be sustainable into the far future and comprehensive action should be taken to minimize this water budget imbalance.

Reduced Soil Macropores and Forest Cover Reduce Warm‐Season Baseflow below Ecological Thresholds in the Upper Delaware River Basin

“…While higher macropore values in the Catskill region resulted in higher low flows with increased forest, other regions, particularly arid climates, and different water budget accounting (e.g., annual vs. seasonal, total volume vs. FDC) have reported that increased forest cover led to decreased low flows (Andréassian ; Wyatt et al ). In some studies, forest cover clearcuts led to greater annual flow volumes via reduced evapotranspiration (Hornbeck et al ; Ellison et al ; Brown et al ), but the land cover change was different from our experiment that exchanged pristine forest and agricultural cover.…”

Effects of afforestation on groundwater recharge and water budgets in the western region of Uruguay

“…Features such as rainfall regimes, soil types, geological conditions, water table depths and alternative land uses affect groundwater balance components and can vary significantly between locations. While some researchers report a reduction in groundwater recharge because of afforestation (Fan et al , ), others report the opposite response (Krishnaswamy et al , ) and others project a mixed response that varies over time (Wyatt et al , ). In this study, groundwater exchanges flows (recharge and discharge) calculated from the afforested DT basin were similar to those found for the pastured LC basin.…”

Forest restoration as a strategy to mitigate climate impacts on wildfire, vegetation, and water in semiarid forests

“…, Wyatt et al. ). Wyatt () found, from a systematic global literature review, an average of 0–50% initial increase in water yield in coniferous forests when basal area is reduced by 5–100%.…”

“…The forests of the United States provide a significant amount of surface water and groundwater supply to the country (Barr 1956), and the connection between watershed land cover and the magnitude and timing of surface water flows has long been recognized (Bosch andHewlett 1982, Robles et al 2017). Recent studies have highlighted the importance of ecosystem health in the contributing area of an aquifer for reliable groundwater resources (Scanlon et al 2005, Wyatt et al 2015. Wyatt (2013) found, from a systematic global literature review, an average of 0-50% initial increase in water yield in coniferous forests when basal area is reduced by 5-100%.…”