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The impact of forest thinning on the reliability of water supply in central Arizona.

Simonit S, Connors JP, Yoo J, Kinzig A, Perrings C - PLoS ONE (2015)

Bottom Line: 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.This represents an estimated net present value of surface water storage of $104 million, considering both water consumption and hydropower generation.

View Article: PubMed Central - PubMed

Affiliation: EcoServices Group, School of Life Sciences, Arizona State University, Tempe, United States of America; International Union for Conservation of Nature (IUCN), Regional Office for Mexico, Central America and the Caribbean, San Josè, Costa Rica.

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.

No MeSH data available.


Related in: MedlinePlus

Estimated drawdown effect of groundwater pumping from SRP wells.a) baseline uptake at year 0; b) maximum groundwater uptake of 325,000 AF year-1.
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pone.0121596.g002: Estimated drawdown effect of groundwater pumping from SRP wells.a) baseline uptake at year 0; b) maximum groundwater uptake of 325,000 AF year-1.

Mentions: The target for alternative water supplies is the difference between annual water demand and the expected surface water supply, and is identified by the annual probability of surface water delivery failure, Gt + Ct = Yqt(zt). The share of groundwater and CAP water supply depends on the ratio of their respective supply costs. Both SRP surface water price (ps) and CAP water price (pc) are assumed to be constant and identified by the values reported in 2013, ps = 14$ AF-1 and pc = 120 $ AF-1. Groundwater prices (pgt), on the other hand, are estimated in terms of variable pumping costs. For the n wells in the SRP service area, the pumping cost is related to the depth of the water table at each well:pgt=∑j=1npkwhEjtQjtn(9)with∑j=1nQjt=Gt(Lxi)(10)Ejt=0.736270Ujtηj(11)Ujt=Hj+∑jhjt(Qjt)(12)where Qjt represents annual groundwater uptake (m3) from the jth well; Ejt is the energy in Kwh/m3 required at each jth well to lift one cubic meter of water to a vertical distance Ujt expressed in meters; pkwh is the unit price of energy assumed at 0.10 $; and 0 ≤ ηj ≤ 1 is the pumping efficiency of the well assumed as 0.90 for all the wells; Hj represents the vertical distance of the water table at the steady state and is taken from a 2006 water table map [38]; and hjt is the aquifer drawdown at time t which is a function of the intersection of the drawdown from the jth well and multiple cones of depression generated by water pumping from neighbouring wells (Fig. 2). Aquifer drawdown at the jth well increases with increasing pumping rate Qjt and it returns to zero when pumping stops. At any time t, pumping rates at each well are estimated from the gap between effective surface water delivery and target supply (Y − St = Gt = ∑jQjt), assuming uniform percentage variation (α) for all wells (i.e. ∑jαQjt = αGt) from the 2006 groundwater pumping data provided for 183 SRP active wells (Fig. 2) within the Phoenix metropolitan area [38]. In doing this we ignore any potential limit to pumping capacity at each well. Eq. (9) says that the price of groundwater is affected by variations in the reliability of surface water supply, thus it is also a function of land cover change in the upstream basin. The aquifer drawdown model is described in S3 File.


The impact of forest thinning on the reliability of water supply in central Arizona.

Simonit S, Connors JP, Yoo J, Kinzig A, Perrings C - PLoS ONE (2015)

Estimated drawdown effect of groundwater pumping from SRP wells.a) baseline uptake at year 0; b) maximum groundwater uptake of 325,000 AF year-1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383454&req=5

pone.0121596.g002: Estimated drawdown effect of groundwater pumping from SRP wells.a) baseline uptake at year 0; b) maximum groundwater uptake of 325,000 AF year-1.
Mentions: The target for alternative water supplies is the difference between annual water demand and the expected surface water supply, and is identified by the annual probability of surface water delivery failure, Gt + Ct = Yqt(zt). The share of groundwater and CAP water supply depends on the ratio of their respective supply costs. Both SRP surface water price (ps) and CAP water price (pc) are assumed to be constant and identified by the values reported in 2013, ps = 14$ AF-1 and pc = 120 $ AF-1. Groundwater prices (pgt), on the other hand, are estimated in terms of variable pumping costs. For the n wells in the SRP service area, the pumping cost is related to the depth of the water table at each well:pgt=∑j=1npkwhEjtQjtn(9)with∑j=1nQjt=Gt(Lxi)(10)Ejt=0.736270Ujtηj(11)Ujt=Hj+∑jhjt(Qjt)(12)where Qjt represents annual groundwater uptake (m3) from the jth well; Ejt is the energy in Kwh/m3 required at each jth well to lift one cubic meter of water to a vertical distance Ujt expressed in meters; pkwh is the unit price of energy assumed at 0.10 $; and 0 ≤ ηj ≤ 1 is the pumping efficiency of the well assumed as 0.90 for all the wells; Hj represents the vertical distance of the water table at the steady state and is taken from a 2006 water table map [38]; and hjt is the aquifer drawdown at time t which is a function of the intersection of the drawdown from the jth well and multiple cones of depression generated by water pumping from neighbouring wells (Fig. 2). Aquifer drawdown at the jth well increases with increasing pumping rate Qjt and it returns to zero when pumping stops. At any time t, pumping rates at each well are estimated from the gap between effective surface water delivery and target supply (Y − St = Gt = ∑jQjt), assuming uniform percentage variation (α) for all wells (i.e. ∑jαQjt = αGt) from the 2006 groundwater pumping data provided for 183 SRP active wells (Fig. 2) within the Phoenix metropolitan area [38]. In doing this we ignore any potential limit to pumping capacity at each well. Eq. (9) says that the price of groundwater is affected by variations in the reliability of surface water supply, thus it is also a function of land cover change in the upstream basin. The aquifer drawdown model is described in S3 File.

Bottom Line: 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.This represents an estimated net present value of surface water storage of $104 million, considering both water consumption and hydropower generation.

View Article: PubMed Central - PubMed

Affiliation: EcoServices Group, School of Life Sciences, Arizona State University, Tempe, United States of America; International Union for Conservation of Nature (IUCN), Regional Office for Mexico, Central America and the Caribbean, San Josè, Costa Rica.

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.

No MeSH data available.


Related in: MedlinePlus