Guilherme F. Marques

Modeling Conjunctive Use Operations and Farm Decisions with Two-Stage Stochastic Quadratic Programming

This paper applies two-stage stochastic quadratic programming to optimize conjunctive use operations of groundwater pump- ing and artificial recharge with farmers expected revenue and cropping decisions. The two-stage programming approach allows modeling of water and permanent crop production decisions, with recourse for uncertain conditions of hydrology, annual crops, and irrigation technology decisions. Results indicate potential gains in expected net benefits and reduction in income variability from conjunctive use, with increase in high value permanent crops along with more efficient irrigation technology.

Economic Value of Storage in Multireservoir Systems

AbstractFollowing three decades of rather low investment in dams, many regions throughout the world are now seeking to further develop new storage capacity to meet exploding demands for water and to hedge against the risk posed by climate change. Storage capacity is often perceived as a key element of climate change adaptation strategies, while at the same time contributing to socioeconomic development through irrigation, energy generation, fish production, and municipal and industrial water supply. The benefits provided by dams must be balanced with the associated environmental and social costs, which can take various forms, such as the degradation of ecosystems because of altered flow regimes and the relocation of people from the impoundment area. The benefits of storage essentially come from the ability to move water in time, making it available during the low-flow season when it becomes more valuable. As river basins develop and new dams are constructed, it may be important for planning and operationa...

Hydroeconomic optimization of integrated water management and transfers under stochastic surface water supply

Efficient reallocation and conjunctive operation of existing water supplies is gaining importance as demands grow, competitions among users intensify, and new supplies become more costly. This paper analyzes the roles and benefits of conjunctive use of surface water and groundwater and market-based water transfers in an integrated regional water system where agricultural and urban water users coordinate supply and demand management based on supply reliability and economic values of water. Agricultural users optimize land and water use for annual and perennial crops to maximize farm income, while urban users choose short-term and long-term water conservation actions to maintain reliability and minimize costs. The temporal order of these decisions is represented in a two-stage optimization that maximizes the net expected benefits of crop production, urban conservation and water management including conjunctive use and water transfers. Long-term decisions are in the first stage and short-term decisions are in a second stage based on probabilities of water availability events. Analytical and numerical analyses are made. Results show that conjunctive use and water transfers can substantially stabilize farmers income and reduce system costs by reducing expensive urban water conservation or construction. Water transfers can equalize marginal values of water across users, while conjunctive use minimizes water marginal value differences in time. Model results are useful for exploring the integration of different water demands and supplies through water transfers, conjunctive use, and conservation, providing valuable insights for improving system management.

Bioenergy Development Policy and Practice Must Recognize Potential Hydrologic Impacts: Lessons from the Americas

Large-scale bioenergy production will affect the hydrologic cycle in multiple ways, including changes in canopy interception, evapotranspiration, infiltration, and the quantity and quality of surface runoff and groundwater recharge. As such, the water footprints of bioenergy sources vary significantly by type of feedstock, soil characteristics, cultivation practices, and hydro-climatic regime. Furthermore, water management implications of bioenergy production depend on existing land use, relative water availability, and competing water uses at a watershed scale. This paper reviews previous research on the water resource impacts of bioenergy production—from plot-scale hydrologic and nutrient cycling impacts to watershed and regional scale hydro-economic systems relationships. Primary gaps in knowledge that hinder policy development for integrated management of water–bioenergy systems are highlighted. Four case studies in the Americas are analyzed to illustrate relevant spatial and temporal scales for impact assessment, along with unique aspects of biofuel production compared to other agroforestry systems, such as energy-related conflicts and tradeoffs. Based on the case studies, the potential benefits of integrated resource management are assessed, as is the need for further case-specific research.

WEAP as a participatory tool for shared vision planning in the River Njoro Watershed in Kenya

This paper presents a preliminary study of the Water Evaluation And Planning System (WEAP) as a decision support tool (DST) for local stakeholders and communities in addressing shared water issues in the River Njoro watershed. Located in the semi-arid Rift Valley of Kenya, the watershed includes important downstream habitat at Lake Nakuru, a large shallow saline lake designated a RAMSAR wetlands site of international importance, and a broad mix of water uses and users. A complex web of possible causes has been put forth by different groups for the growing water quality and quantity problems. Most attention has been focused on recent deforestation in the upper catchment. The magnitude, extent and duration of water shortage problems and their causes, however, have been poorly documented and poorly understood, hindering pursuit of more sustainable and effective options for water resource management and development. Lacking is a common understanding of the water system and a clear definition of the problems faced by different stakeholders, in part because no comprehensive quantitative assessment of the water supply and demand system has been undertaken. In this exploratory study, a model of the Njoro watershed using WEAP was created and a workshop held with a multi-disciplinary group of Kenyan researchers involved in local water and environmental issues. The workshop explored WEAP’s potential as a participatory modeling tool to support Njoro watershed stakeholders to develop a shared vision of water management solutions. Modeling capabilities and features of WEAP are assessed and its usefulness as a DST considered for a developing country watershed such as the Njoro. Outcomes of the workshop included new information and increased common knowledge about the current water resources system, and new shared insights into the causes of water problems and potential solution strategies. These represent important stakeholder educative and attitudinal changes that support a shared vision of solutions and consensus on sustainable and cooperative water management.

Hydroeconomic Models as Decision Support Tools for Conjunctive Management of Surface and Groundwater

Conjunctive use (CU) of surface and groundwater storage and supplies is essential for integrated water management. It is also a key strategy for supporting groundwater-dependent ecosystems, and for adapting water systems to future climate and land use changes. CU has become increasingly sophisticated and integrated with other innovative and traditional water management techniques, such as water transfers, water reuse, demand management, and aquifer remediation. CU adds value for society (increasing average yield and reliability) but can also induce costs to some parties, such as damaging senior water rights of surface water users when pumping from the aquifer reduces streamflow. Groundwater overexploitation also can produce a host of undesirable economic and environmental impacts. Successful CU implementation typically requires changes in infrastructure and operations, but also changes in institutions and institutional arrangements to offset potential third party costs and protect ecosystems. This chapter analyses first the management and economic implications of CU, addressing advantages, costs and limitations, as well as the potential contribution of economic instruments to the conjunctive operation of groundwater and surface storage and resources. CU management models are then classified according to the CU problem, their formulation and solution techniques. Different applications of hydroeconomic models are reviewed in a wide range of CU problems. A few applications are discussed more in-depth, using cases from California and Spain. Then, we discuss the relevance of these models in decision-making, and the policy and institutional implications. Finally, we address limitations and challenges, and suggest future directions.

Multistage Stochastic Optimization for Agricultural and Urban Water Management with Imperfect Forecasts

Long-term hydrologic forecasts are not widely used in water resource decision-making practices, partially due to the large forecast uncertainty involved. This paper formulates how long-term (annual) hydrologic forecasts might improve the management decisions of an integrated regional water resources system, using a three-stage stochastic optimization model. The three stage model is developed based on a two-stage model, which the paper also examines analytically. Both models incorporate decisions regarding crop mix, irrigation technology, conjunctive surface and ground water operation, urban water conservation, and water transfers between the agricultural and urban areas. The first stage includes all permanent decisions, such as acreage of perennial crops and urban conservation measures that will exist for multiple years. The second stage consists of temporary decisions, like acreage of annual crops, annual urban conservation measures and annual water transfers, whose impacts are limited within a year, based on imperfect forecast information. The third stage of the three-stage model comprises recourse decisions that “adjust” the temporary decisions in the second stage based on the “realizations” of hydrology which are conditional on each of the year type forecast employed in the second stage.