The Impact of Forest Thinning on the Reliability of Water Supply in Central Arizona

Abstract

Economic growth in Central Arizona, as in other semiarid systems characterized by low and variable rainfall, has historically depended on the effectiveness of strategies to manage water supply risks. Traditionally, the management of supply risks includes three elements: hard infrastructures, landscape management within the watershed, and a supporting set of institutions of which water markets are frequently the most important. In this paper we model the interactions between these elements. A forest restoration initiative in Central Arizona (the Four Forest Restoration Initiative, or 4FRI) will result in thinning of ponderosa pine forests in the upper watershed, with potential implications for both sedimentation rates and water delivery to reservoirs. Specifically, we model the net effect of ponderosa pine forest thinning across the Salt and Verde River watersheds on the reliability and cost of water supply to the Phoenix metropolitan area. We conclude that the sediment impacts of forest thinning (up to 50% of canopy cover) are unlikely to compromise the reliability of the reservoir system while thinning has the potential to increase annual water supply by 8%. This represents an estimated net present value of surface water storage of $104 million, considering both water consumption and hydropower generation.

Observed Hydrologic Impacts of Landfalling Atmospheric Rivers in the Salt and Verde River Basins of Arizona, United States

“…With a population of over four million people, the Phoenix metro area in Arizona is the sixth largest metropolis in the United States; it is estimated that by the year 2030 the population will exceed six million (http:// www.census.gov). The SVRB (Figure 1) contribute to approximately 93% of the Phoenix metro area's annual water supply, approximately 2,837 million m 3 , drawn from a system of six reservoirs that store snowmelt runoff resulting from winter precipitation (Svoma, 2011), while the remaining 7% is provided by groundwater (Simonit et al, 2015). The basins are also important for two Native American tribes that rely heavily on the basins' natural resources for their livelihood and for numerous wilderness areas.…”

A review of economic approaches modeling the complex interactions between forest management and watershed services

“…In contrast, more than 40% of the studies use physically-based hydrological models to quantify the effect of forest management or forest conservation on the provision of a single or multiple watershed services. Physically-based hydrological models are used to simulate either spatially distributed surface run-off, ground water recharge and sediments loads (Arias et al, 2011;Fan et al, 2016;Ovando et al, 2017;Quintero et al, 2009;Simonit et al, 2015), or to estimate lumped water balance figures (Duncker et al, 2012;Garcia-Prats et al, 2016;Nordblom et al, 2010). Other studies use a set of conceptual or empirically calibrated hydrological functions to represent both hydrological and sedimentation processes.…”

“…Other studies use a set of conceptual or empirically calibrated hydrological functions to represent both hydrological and sedimentation processes. The parameters of these functions are either taken from existing literature (Eriksson et al, 2011;Nordblom et al, 2012;Susaeta et al, 2017) or quantified using primary data collected in the case study area (Kramer et al, 1997;Simonit et al, 2015).…”

A Multiyear Assessment of Irrigation Cooling Capacity in Agricultural and Urban Settings of Central Arizona

“…Irrigation water supply is typically limited under the arid conditions of the region and is sensitive to land cover change and climate variations (Gober and Kirkwood 2010;Simonit et al 2015). In addition, municipal water demand, which is correlated with summer temperature (Balling et al 2008;Opalinski et al 2020), may also increase in a warmer future.…”