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Optimal groundwater management when recharge is declining: a method for valuing the recharge benefits of watershed conservation

Demand for water will continue to increase as per capita income rises and the population grows, and climate change can exacerbate the problem through changes in precipitation patterns and quantities, evapotranspiration, and land cover—all of which directly or indirectly affect the amount of water that ultimately infiltrates back into groundwater aquifers. We develop a dynamic management framework that incorporates alternative climate-change (and hence, recharge) scenarios and apply it to the Pearl Harbor aquifer system on O‘ahu, Hawai‘i. By calculating the net present value of water for a variety of plausible climate scenarios, we are able to estimate the indirect value of groundwater recharge that would be generated by watershed conservation activities. Enhancing recharge increases welfare by lowering the scarcity value of water in both the near term and the future, as well as delaying the need for costly alternatives such as desalination. For a reasonable range of parameter values, we find that the present value gain of maintaining recharge ranges from 31.1million to over1.5 billion.

Published version: Burnett, K. and Wada, C.A., 2014. Optimal groundwater management when recharge is declining: a method for valuing the recharge benefits of watershed conservation. Environmental Economics and Policy Studies. In Press.


Integrating Demand-Management with Development of Supply-Side Substitutes

Sustaining water availability at current prices in the face of growing demand and declining resources is not possible, and scarcity is further exacerbated by falling recharge levels due to climate change, urbanization, and watershed depreciation. We discuss an integrated approach to water-resource development based on principles of sustainability science. In addition to demand management such as pricing, we consider supply-side substitutes such as desalination and wastewater recycling. The importance of integrating demand- and supply-side approaches is especially evident in the case of watershed conservation as climate adaptation. Watershed conservation reduces scarcity by improving groundwater recharge. Yet, incorrect pricing can waste those potential gains. We discuss a joint management strategy, wherein block prices for groundwater consumption and co-determined prices for watershed conservation incentivize and finance efficient profiles of both.


Ordering Extraction from Multiple Aquifers

Optimal groundwater extraction satisfies the condition that the marginal benefits of water consumption equal the full marginal cost of extraction in each period, including the opportunity cost of future benefits foregone. But how should this well-known condition be generalized when there are multiple aquifers available? We provide an extension of the “Pearce equation” to guide the optimal ordering of resource extraction and an illustrative application wherein it is optimal to extract from the “leakiest” aquifer first, letting another aquifer increase in volume. This generalized least cost-first principle contrasts strongly with the sustainable yield approach. By including spatial dimensions, the model provides the marginal valuations of water at each time and place, such that full marginal cost pricing can incentivize users to implement the efficient program. While an untrammeled water market would fail to provide the optimal solution, regulators can facilitate efficient water trading by setting appropriate exchange rates.


Intergenerational Equity with Individual Impatience in an OLG Model of Optimal and Sustainable Growth

Among the ethical objections to intergenerational impartiality is the violation of consumer sovereignty given that individuals are impatient. We accommodate that concern by distinguishing intra- and inter-generational discounting in an OLG model suitable for analyzing sustainability issues. Under the assumption of constant elasticity of marginal felicity, the optimum trajectory of aggregate consumption is guided, via the Ramsey condition, by the intergenerational discount rate but not the personal discount rate. In an economy with produced capital and a renewable resource, intergenerational neutrality results in a sustained growth path, without the necessity of a sustainability constraint, even in the presence of intragenerational impatience. We also find that green net national product remains constant along the optimal approach path to golden rule consumption.

Published version: Endress, L.H., Pongkijvorasin, S., Roumasset, J., Wada, C.A., 2013. Intergenerational equity with individual impatience in a model of optimal and sustainable growth. Resource and Energy Economics. In Press.


The Economic Impact of the University of Hawai'i System

The University of Hawai‘i (UH) generates economic activity through its purchases from local businesses, its payment to its employees, and spending by students and visitors. This report estimates UH’s total economic activity in the state of Hawai‘i in fiscal year 2012. Following a standard approach, we define economic impact to be the direct, indirect, and induced economic activities generated by the university’s spending in the state economy.

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A dynamic approach to PES pricing and finance for interlinked ecosystem services: Watershed conservation and groundwater management

A theory of payment for ecosystem services (PES) pricing consistent with dynamic efficiency and sustainable income requires optimized shadow prices. Since ecosystem services are generally interdependent, this requires joint optimization across multiple resource stocks. We develop such a theory in the context of watershed conservation and groundwater extraction. The optimal program can be implemented with a decentralized system of ecosystem payments to private watershed landowners, financed by efficiency prices of groundwater set by a public utility. The theory is extended to cases where land is publicly owned, conservation instruments exhibit non-convexities on private land, or the size of a conservation project is exogenous. In these cases, conservation investment can be financed from benefit taxation of groundwater consumers. While volumetric conservation surcharges induce inefficient water use, a dynamic lump-sum tax finances investment without distorting incentives. Since the optimal level of conservation is generated as long as payments are correct at the margin, any surplus can be returned to consumers through appropriate block pricing. The present value gain in consumer surplus generated by the conservation-induced reduction in groundwater scarcity serves as a lower bound to the benefits of conservation without explicit measurement of other benefits such as recreation, biodiversity, and cultural values.


Published Version: Roumasset, J., Wada, C.A., 2013. A dynamic approach to PES pricing and finance of interlinked ecosystem services: Watershed conservation and groundwater management. Ecological Economics. 87, 24-33.




The Contribution of the University of Hawai‘i at Manoa to Hawai‘i’s Economy in 2012

The University of Hawai‘i at Mānoa (UHM) generates economic activity through its purchases from local businesses, its payment to its employees, and spending by students and visitors. This report estimates UHM’s total economic activity in the state of Hawai‘i in fiscal year 2012. Following a standard approach, we define economic impact to be the direct, indirect, and induced economic activities generated by the university’s spending in the state economy.

Although one can think of the UHM as if it were one of many businesses or industries in Hawai‘i, an important difference between UHM and most private businesses is that UHM gets a substantial part of its funding from taxpayers. In FY2012, UHM and the supporting RCUH (Research Corporation of the University of Hawai‘i) spent a total of $878 million in support of its education mission; the State General Fund paid $198 million of the total. Adding money spent by the privately funded UH Foundation, spending by students, out-of-town visitor spending related to UHM sponsored professional meetings and conferences brings total UHM-related expenditures to $1.40 billion in FY2012, 90% of which was spent locally.

Overall, the $1.40 billion of education-related expenditures attributable to UHM generated $2.45 billion in local business sales, $735 million in employee earnings, $131 million in state tax revenues, and slightly under 20,000 jobs in Hawai‘i in FY2012. This represented approximately 3.4% of total jobs, 2.5% of worker earnings, and 2.2% of total state tax revenues.

Looking to the future, the university’s Hawai‘i Innovation Initiative ( HI2 ) plans to more than double the UH system’s current level of extramural research funds from less than $500 million to an ambitious $1 billion per annum. If the HI2 successfully doubles research expenditures, our analysis suggests more than 5,000 new jobs would be created from the ripple effects of the research spending alone, independent of any technology transfer and other jobs created as a direct result of the research.


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The Economics of Groundwater

We provide synthesis of the economics of groundwater with a focus on optimal management and the Pearce equation for renewable resources. General management principles developed through the solution of a single aquifer optimization problem are extended to the management of multiple resources including additional groundwater aquifers, surface water, recycled wastewater, and upland watersheds. Given an abundant (albeit expensive) substitute, optimal management is sustainable in the long run. We also discuss the open-access equilibrium for groundwater and the conditions under which the Gisser-Sanchez effect (the result that the present value generated by competitive resource extraction and that generated by optimal control of groundwater are nearly identical) is valid. From the models and examples discussed, one can conclude that optimization across any number of dimensions (e.g. space, time, quality) is driven by a system shadow price, and augmenting groundwater with available alternatives lessens scarcity and increases welfare if timed appropriately. Other rules-of-thumb including historical cost recovery, independent management of separate aquifers, and maximum sustainable yield are inefficient and may involve large welfare losses.

Working Paper

Foundations for Hawai‘i’s Green Economy: Economic Trends in Hawai‘i Agriculture, Energy, and Natural Resource Management

It is clear from previous studies that Hawai‘i’s natural capital is highly valued and should be managed accordingly. For example, Kaiser et al. (1999) estimate that the Ko‘olau watershed provides forest benefits valued between $7.4 and $ 14 billion, comprised of water resource benefits ($4,736-­‐9,156 million), species habitat benefits ($487-­‐1,434 million), biodiversity benefits ($0.67-­‐5.5 million), subsistence benefits ($34.7-­‐131 million), hunting related benefits ($62.8-­‐237 million), aesthetic values ($1,040-­‐3,070 million), commercial harvest ($0.6-­‐2.4 million), and ecotourism ($1,000-­‐2,980 million). Hawai‘i’s coral reefs alone are estimated to generate at least $10 billion in present value, or $360 million per annum (Cesar and van Beukering, 2004). Another recent study considering the value to all U.S. households finds that increasing the current size of marine protected areas in Hawai‘i from 1% to 25% and restoring five acres of coral reefs annually would generate $34 billion per year (Bishop et al., 2011).2 While many studies that place value on Hawai‘i’s natural resources have been undertaken in recent years, little is known about the economic impacts generated by agencies charged with protecting and managing these important resources in Hawai‘i. To that end, an online survey of natural resource managers in Hawai‘i was conducted, and the results are summarized in section 6 of this report.


Foundations for Hawai‘i’s Green Economy: Economic Trends in Hawai‘i Agriculture, Energy, and Natural Resource Management

This report provides the first comparison of standard economic indicators for three sectors that are key to future sustainability in Hawai‘i - renewable energy, agriculture and natural resource management. Economic information has long been collected for many sectors in Hawai‘i, including agriculture and energy, but no systematic surveys have been conducted on the NRM sector to date. With support from The Nature Conservancy and Hau‘oli Mau Loa Foundation, the University of Hawai‘i Economic Research Organization was tasked with characterizing this important part of Hawai‘i’s economy, in terms of number and types of jobs, salaries, and annual expenditures.


Economic Analysis of the Proposed Rule to Prevent Arrival of New Genetic Strains of the Rust Fungus Puccinia psidii in Hawai‘i

Since its first documented introduction to Hawai‘i in 2005, the rust fungus P. psidii has already severely damaged Syzygium jambos (Indian rose apple) trees and the federallyendangered Eugenia koolauensis (nioi). Fortunately, the particular strain has yet to cause serious damage to ‘ōhi‘a, which comprises roughly 80% of the state’s native forests and covers 400,000 ha. Although the rust has affected less than 5% of Hawaii’s ‘ōhi‘a trees thus far, the introduction of more virulent strains and the genetic evolution of the current strain are still possible. Since the primary pathway of introduction is Myrtaceae plant material imported from outside the state, potential damage to ‘ohi‘a can be minimized by regulating those high-risk imports. We discuss the economic impact on the state’s florist, nursery, landscaping, and forest plantation industries of a proposed rule that would ban the import of non-seed Myrtaceae plant material and require a one-year quarantine of seeds. Our analysis suggests that the benefits to the forest plantation industry of a complete ban on non-seed material would likely outweigh the costs to other affected sectors, even without considering the reduction in risk to ‘ōhi‘a. Incorporating the value of ‘ōhi‘a protection would further increase the benefit-cost ratio in favor of an import ban.

Working Paper

Islands of Sustainability in Time and Space

We review the economics perspective on sustainable resource use and sustainable development. Under standard conditions, dynamic efficiency leads to sustainability of renewable resources but not the other way around. For the economic‐ecological system as a whole, dynamic efficiency and intergenerational equity similarly lead to sustainability, but ad hoc rules of sustainability may well lead to sacrifices in human welfare. We then address the challenges of extending economic sustainability to space as well as time and discuss the factors leading to optimal islands of preservation regarding renewable resources. Exogenous mandates based on moral imperatives such as self‐sufficiency and strong sustainability may result in missed win‐win opportunities that could improve both the economy and the environment, as well as increase social welfare across generations.


Efficient Management of Coastal Marine Nutrient Loads with Multiple Sources of Abatement Instruments

Pollution management based on marginal abatement costs is optimal only if those abatement costs are specified correctly. Using the example of nitrogen pollution in groundwater, we show that the marginal abatement cost function for any given pollution source can be directly derived from a social-welfare maximization problem, wherein controls include both abatement instruments and inputs to pollution-generating production of a good or service. The solution to the optimization model reveals that abatement instruments for each source should be used in order of least marginal abatement cost, and the sources should in turn abate in order of least cost. The least-cost result remains optimal, even when the abatement target is exogenously determined.

Working Paper

Ordering Renewables: Groundwater, Recycling and Desalination


Optimal recycling of minerals can be thought of as an integral part of the theory of the mine. In this paper, we consider the role that wastewater recycling plays in the optimal extraction of groundwater, a renewable resource. We develop a two-sector dynamic optimization model to solve for the optimal trajectories of groundwater extraction and water recycling. For the case of spatially increasing recycling costs, recycled water serves as a supplemental resource in transition to the steady state. For constant unit recycling cost, recycled wastewater is eventually used as a sector-specific backstop for agricultural users, while desalination supplements household groundwater in the steady state. In both cases, recycling water increases welfare by shifting demand away from the aquifer, thus delaying implementation of costly desalination. The model provides guidance on when and how much to develop resource alternatives.


Optimal Provision and Finance of Ecosystem Services: the Case of Watershed Conservation and Groundwater Management

Payments for ecosystem services should be informed by how both the providing-resource and the downstream resource are managed. We develop an integrated model that jointly optimizes conservation investment in a watershed that recharges a downstream aquifer and groundwater extraction from the aquifer. Volumetric user-fees to finance watershed investment induce inefficient water use, inasmuch as conservation projects actually lower the optimal price of groundwater. We propose a lump-sum conservation surcharge that preserves efficient incentives and fully finances conservation investment. Inasmuch as proper watershed management counteracts the negative effects of water scarcity, it also serves as adaptation to climate change. When recharge is declining, the excess burden of non-optimal watershed management increases.

working paper


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