Journal of Water Resources Planning and Management

The assessment of stormwater runoff pollution from urban catchments is addressed within a probabilistic framework. The methodology utilizes probability density functions of rainfall event characteristics, a runoff coefficient based rainfall-runoff transformation, and commonly used pollutant buildup and washoff processes representations. Employing derived probability distribution theory, analytical probabilistic runoff quality models are derived using exponential buildup and washoff functions. The derived analytical models yield expressions for expected event pollutant washoff load, annual average washoff load, the probability distribution of event washoff load, and the long-term average pollutant event mean concentration (EMC). These derived models are verified with available field data from an urban catchment located in the Greater Toronto Area. The verification results suggest that these analytical probabilistic models can be used for the assessment of runoff pollutant loads from urban catchments during planning-level analyses. These are computationally efficient closed-form mathematical expressions that can be easily incorporated into the spreadsheets and are thus a useful tool as an alternative or complement to more resource-intensive simulation models.

Accurate prediction of the current and future conditions of wastewater systems using available assessment data is crucial for developing appropriate proactive maintenance and rehabilitation strategies for an aging wastewater collection and conveyance system. This paper proposes a method to estimate the transition probabilities of different condition states in Markov chain-based deterioration models for wastewater systems using an ordered probit model. The proposed model is applied and evaluated using the condition data of sewer pipes managed by the City of San Diego’s Metropolitan Wastewater Department. The developed model presents some advantages in estimating transition probabilities over the approaches developed in the past, including the nonlinear optimization-based approach, in terms of versatility in the implementation, precision of the estimated data, and appropriateness of the assumptions in the model. The paper concludes that the ordered probit model approach is a statistically sound and robust method; however, in order to gain greater accuracy in deterioration modeling, periodic assessment of the wastewater systems with more data types is desirable.

Six balancing rules are derived to inform short-term drawdown and recharge of water in multiple, unconnected aquifers. Management objectives are: (1) minimizing costs; (2) maximizing duration of operation; and (3) maximizing accessibility as a tradeoff between maximizing instantaneous withdrawal rate and the duration to sustain withdrawals. Engineering optimization formulations use either a specified target delivery rate (for withdrawals) or available surface water supply (to recharge). Aquifers are modeled as separate, single-celled basins with lumped parameters representing key physical, institutional, and financial characteristics. Each formulation is solved analytically for the case where constraints are nonbinding. Solutions are explained as operating rules. Two examples confirm the analytical solutions. The results show how cost characteristics, fraction of recharged water available for withdrawal (fractional recovery), initial storage, maximum recharge and pumping rates, and uncertainties regarding the future availability of water for extraction influence recharge and withdrawal decisions.

This paper evaluates the downstream hydrologic and economic impacts of development strategies that promote greater on-site storage of storm water. This paper applies a methodology to a specific case study that emphasizes flood risk reduction and drainage infrastructure. The estimates are at a first level of approximation. We use widely accepted simulation models and available data to compare alternative development scenarios for the 0.01 annual probability storm event. For a watershed in a rapidly developing area near Chicago, Ill., reduced downstream flooding with the employment of conservation design practices generates from $\$0\text{to}\mathrm{19,400}∕\mathrm{ha}$ $(\$0–\mathrm{7,800}∕\text{acre})$ in downstream property value benefits over all affected areas. For comparison purposes, flood-damage estimation methods generate an average of $\$\mathrm{16,800}–\$\mathrm{24,200}∕\mathrm{ha}$ $(\$\mathrm{6,700}–\$\mathrm{9,700}∕\text{acres}$ present value reduction in damages for the 0.01 probability flood event alone. The two methods yield conservative, but mutually reinforcing estimates. For infrastructure benefits, considering only downstream road culverts, the use of conservation design techniques upstream avoids $3.3 million in costs of culvert replacement or upgrades. The sum of the downstream flood mitigation and infrastructure benefits amounts to $920–1,440/developed hectares ($380–590/developed acres) following conservation design practices.

The purpose of this paper is to optimize the preliminary selection, sizing and placement of hydraulic devices in a pipeline system in order to control its transient response. A global optimal solution is sought using both genetic algorithm (GA) and particle swarm optimization (PSO) approaches involving an unknown combination of hydraulic devices to cope effectively with water hammer conditions. In this exploratory study, three simple objective functions are considered: (1) to minimize the maximum head; (2) to maximize the minimum head; and (3) to minimize the difference between the maximum head and minimum head in the system. Several case studies are tested numerically using different protection strategies. This study shows that the integration of a GA or PSO with a transient analysis technique can improve the search for hydraulic protection devices in a pipe network. This study also shows that the selection of an optimum protection strategy is an integrated problem, involving consideration of loading conditions, device and system characteristics, and protection strategy. Significantly, simpler transient control strategies are often found to perform better than more complex ones.

This study investigates recreation use value for access to a Sonoran Desert canyon, and associated instream flow, through a case study of Aravaipa Canyon Wilderness. The Wilderness is one of the last perennial streams in Southern Arizona, tributary to the famed and imperiled San Pedro River. Available permit information is combined with zip-code level census data to estimate a zonal travel cost model of recreation trip demand. Estimated consumer surplus per visitor day values are $25.06 and $17.31 (in 2003 dollars), for two separate access sites. Results indicate a significant recreation value of surface water sites in the Sonoran Desert region, while the value discrepancy may imply a premium for remote recreation.