Archive for the ‘Article Highlights’ Category

GIS for variable source area

Tuesday, January 17th, 2012

February 2012 Article (Early View): “Incorporating Variable Source Area Hydrology into a Spatially Distributed Direct Runoff Model,” by Brian Buchanan, Zachary M. Easton, Rebecca Schneider, and M. Todd Walter.

Representative maps

This paper describes a geographic information system-based operational model that simulates the spatio-temporal dynamics of variable source area (VSA) runoff generation and distributed runoff-routing, including through complex artificial drainage networks. The model combines the Natural Resource Conservation Service’s Curve Number (CN) equation for estimating storm runoff with the topographic index concept for predicting the locations of VSA and a runoff-routing algorithm into a new spatially distributed direct hydrograph model.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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SWAT in Canada

Thursday, January 12th, 2012

February 2012 Article (Early View): “Modeling Climate Change Impacts on Hydrology and Nutrient Loading in the Upper Assiniboine Catchment,” Rajesh R. Shrestha, Yonas B. Dibike, and Terry D. Prowse.

Lake Winnipeg Watershed

The authors employed the SWAT model for future (2042-2062) periods with model forcings for future climates derived from three regional climate models and their ensemble means. The effects of future changes in climatic variables, especially precipitation and temperature, are clearly evident in the resulting snowmelt and runoff regimes. The future hydrologic scenarios consistently show earlier onsets of spring snowmelt and discharge peaks, and higher total runoff volumes. The simulated nutrient loads closely match the dynamics of the future runoff for both nitrogen and phosphorus, in terms of earlier timing of peak loads and higher total loads. However, nutrient concentrations could decrease due to the higher rate of runoff increase.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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BMP’s and climate change

Tuesday, January 10th, 2012

February 2012 Article: “Sensitivity Analysis of Best Management Practices Under Climate Change Scenarios,” by Sean A. Woznicki and A. Pouyan Nejadhashemi.

“The results of this research suggest that the majority of agricultural BMPs tested in this study are significantly sensitive to climate change.” That ought to get your attention!

The objective of this study was to perform a sensitivity analysis of BMPs across future climate change scenarios for the Tuttle Creek Lake watershed (TCLW) of Kansas and Nebraska using Soil and Water Assessment Tool (SWAT) 2009 model. Eight agricultural BMPs and a baseline scenario were implemented within SWAT for each of four climate scenarios.

The results show too many details for a quick summary here. You’ll have to read the article to learn about any particular method. The lesson, though, is that BMP’s are sensitive to climate changes, and the effect varies for the particular BMP.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Regionalization for flow duration

Friday, January 6th, 2012

February 2012 Article (Early View): “Evaluation of a Regionalization Approach for Daily Flow Duration Curves in Central and Southern California Watersheds,” by Allen Hope and Ryan Bart.

Here’s another example of a negative result that still yields important insights.

The abstract: “Discontinuities in flow regimes of ephemeral rivers in California make the modeling of daily flow duration curves (FDCs) in ungauged watersheds challenging. A regionalization approach previously developed for perennial and ephemeral watersheds in Portugal was tested in central and southern California. This approach, which is based on the theory of total probability, requires the prediction of three key flow variables in ungauged watersheds: the percentage of time the river is dry, the nonzero flow equalled or exceeded 80% of the time, and the mean daily flow for nonzero flows. Data from 41 watersheds in California were used to develop and validate regression equations for these three metrics. The methodology included an “all possible models” regression approach, an extensive set of watershed descriptors as potential independent variables, and two different methods for constructing observed FDCs. Suitable regression models could not be identified for predicting any of the required flow metrics. The contrasting results from the studies in Portugal and California were primarily attributed to differences in the aridity of watersheds in the two samples.”

Why? The poor performance of the approach in California compared to the more promising results in Portugal may be a consequence of the more arid conditions typical of watersheds in central and southern California. Despite the large number of variables used to characterize watersheds, it was not possible to identify controls over the number of zero flow days in the California watersheds. Understanding these controls and formulating equations to predict low-flow metrics may be one of the most critical challenges in establishing a regionalization procedure for FDCs in this region. Furthermore, future studies may examine mathematical models to describe the FDCs with regression equations based on watershed morphological and/or climatic variables to predict the parameters of these models.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Great Miami Water Quality Trading Program

Wednesday, January 4th, 2012

February 2012 Article (Early View): “An Ex Post Evaluation of Ohio’s Great Miami Water Quality Trading Program,” by David A. Newburn and Richard T. Woodward.

Market-based approaches to address water quality problems have resulted in only limited success, especially in trading programs involving both point and nonpoint sources. This article analyzes one of the largest point-nonpoint trading programs – the Great Miami Trading Program (GMTP) in Ohio, administered by the Miami Conservancy District (MCD). The evaluation focuses on the economic and institutional aspects of the program, including cost effectiveness, efficiency of bidding, transaction costs, trading ratios, and innovation.

The GMTP is one of the most successful trading programs to date in several dimensions: the program has resulted in significant demand for pollution credits from WWTPs, these sources have purchased credits from nonpoint sources, and the program has led to the implementation of a large number and diverse array of agricultural best management practices (BMPs) to reduce pollution in the watershed.

The study found that the MCD’s reliance on county-level SWCD offices to recruit and advise farmers has been essential to achieve relatively high rates of farmer participation. Additionally, the MCD is able to partly free ride on the administrative costs that SWCD offices receive to assist federal conservation programs, which is helpful to lower costs for a fledgling trading program. However, the involvement of SWCD offices reduced the potential cost savings from the reverse auction structure because some agents were able to learn about the threshold price over the six rounds of bidding and help farmers bid strategically. Overall, the program structure serves as an effective model for future trading programs in other regions that seek to involve agricultural nonpoint sources.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Decentralized groundwater recharge

Tuesday, January 3rd, 2012

February 2012 Article (Early View): “Decentralized Groundwater Recharge Systems Using Roofwater and Stormwater Runoff,” by Daniel B. Stephens, Mark Miller, Stephanie J. Moore, Todd Umstot, and Deborah J. Salvato.

Conceptual Diagram of Water Balance Components for (a) an Undeveloped Site and (b) a Home Site With Low-Impact Development Technology.

This article assesses the importance of decentralized methods to reduce stormwater runoff, including methods such as low-impact development (LID) technology, and to enhance recharge in urban areas. For urban watersheds with net excess runoff, the authors examine the role for more widely distributed, artificial recharge systems at the home lot, subdivision, neighborhood, shopping mall, or business park scale, using captured roof or hardscape runoff to gradually replenish groundwater supplies without adding significant new large-scale infrastructure.

In this conceptual model of a decentralized urban recharge system, runoff is limited to the predevelopment condition. Thus, on a partially hardscaped lot, the water volume that could be salvaged from runoff would then be the precipitation minus the predevelopment runoff, minus natural recharge and evapotranspiration. Capturing runoff close to its source helps minimize dissolved chemicals or entrained sediment in runoff. By encouraging LID options that favor recharge, the benefits double; that is, groundwater storage increases and surface water quality improves.

Costs to implement decentralized systems seem to be favorable in comparison to centralized and heavily engineered systems, but, the authors note, there are few incentives currently in place to encourage public support; consequently, implementation is likely to be a slow process. Nevertheless, there is evidence that a movement toward decentralized systems may have already begun, as some municipalities, counties, states, and now likely federal facilities have begun to encourage or mandate groundwater recharge from stormwater at the local scale to a great extent.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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A simple water balance model

Monday, January 2nd, 2012

February 2012 Article (Early View): “Prediction of Streamflow Regime and Annual Runoff for Ungauged Basins Using a Distributed Monthly Water Balance Model,” by R.D. (Dan) Moore, J.W. Trubilowicz, and J.M Buttle.

(I really love a good abstract, so I’m just going to copy this one here!)

Prediction of streamflow in ungauged basins is a global challenge, but is particularly an issue in physiographically complex regions like British Columbia (BC), Canada. The objective of this study was to assess the accuracy of a simple water balance model that can be run using existing spatial datasets. The model was developed by modifying an existing monthly water balance model to account for interception loss from forest canopy, glacier melt, and evaporation from lakes. The model was run using monthly climate normals from the ClimateBC application, which have a horizontal resolution of 400 m. Each ClimateBC grid cell was classified as forest, open land, glacier or water surface based on provincial scale digital maps of biogeoclimatic zones, glaciers, and water. The output was monthly mean runoff from each grid cell. These values were integrated within the catchment boundaries for streams gauged by the Water Survey of Canada. Annual runoff was predicted with modest accuracy: after updating the predicted runoff by interpolating errors from neighboring gauged streams, the mean absolute error was 25.4% of the gauged value, and 52% of the streams had errors less than 20%. However, the model appears to be quite robust in distinguishing between pluvial, hybrid, and melt-dominated hydroclimatic regimes, and therefore has promise as a tool for catchment classification.

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Why do some watershed groups succeed?

Tuesday, December 27th, 2011

February 2012 article (Early View): “Collaborative Watershed Groups in Three Pacific Northwest States: A Regional Evaluation of Group Metrics and Perceived Success,” by B.C. Chaffin, R.L. Mahler, J.D. Wulfhorst, and B. Shafii.

A lot of water policy research concerns regional and national policies and decisions of high-level muckety mucks. This paper is an example of a different policy theme I saw developing at the AWRA Annual Conference in November 2011. It looks at how group members interact at the local level, and how this interaction can be improved.

Why do some watershed groups succeed and other not? This paper uses data collected from a survey instrument to determine the status, structure, and success of watershed groups in Idaho, Oregon, and Washington, respectively.

The authors analyzed the extent to which leadership roles and participant satisfaction within PNW watershed groups act as key factors in the groups’ perceived levels of success. They also compared satisfaction levels of six internal core factors (funding, membership, motivation, leadership, mission, and data availability) and related effects upon watershed groups’ perceived levels of success.

They observed a significant positive association between perceived watershed group success and the following watershed group metrics: watershed group funding activities, number of members in a watershed group, motivation of watershed group members, leadership within the watershed group, group mission, and availability of necessary watershed data. It is therefore reasonable to believe that ensuring or increasing group member satisfaction with these internal elements of group structure and function will increase perceived watershed group success.

Overall, watershed groups with clear missions and goals are likely to be more successful than those groups with a lost or unclear focus.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Crop discharge permits

Monday, December 26th, 2011

February 2012 Article (Early View): “Crop Discharge Permits for Reduction of Nitrogen Loads to the Baltic Sea,” by Dennis Collentine and Holger Johnsson

A major share of the anthropogenic nitrogen loads coming from the countries around the Baltic Sea originate from farmland. This article describes how a permit system based on the composite market model can be used to evaluate measures that create a demand for permits from nonpoint agricultural sources.

Markets in the Composite Market Model.

The composite market model disaggregates permit transactions into two primary markets and one secondary market with a central role played by a regulatory authority. A system based on three markets allows permit transactions to be separated into individual functional components. This separation into functions allows each of these markets to be developed independently while at the same time contributing information from the transactions to the other markets.

The demand for discharge permits is dependent on regulation. Policies targeting pollution reduction based on economic incentives need to include an element of source control to create markets. Only when discharge sources are forced by regulation to either choose to purchase a permit or cease the load generating activity will there be demand for permits. Requiring a discharge permit for cultivation of particular crops is one form of regulation.

The effect of implementing crop discharge permits are studied on two scales. In the first of these two, retention estimates are available at a high degree of resolution so that estimates can be made of the change in the net load of N from requiring crop discharge permits. On a broader regional scale, while changes in leaching from requiring permits can only be estimated for gross N loads, this scale gives a better indication of the potential for crop permits to meet the reduction targets.

This study demonstrates how the proposed permit system can generate measures that lead to cost efficient reduction of N loads to the Baltic Sea. It is possible to estimate the reduction in N leaching from implementing a system that required discharge permits for cultivation of specific crops. While this reduction is a result of regulation, the proposed permit system allows agricultural producers flexibility in complying with the regulation by allowing a permit to be held that corresponds to the marginal cost of abatement. The advantage is although the regulation achieves the expected reduction the permit system allows for a cost efficient response. The cost to producers creates an economic incentive to allocate crop production in a cost efficient way. The requirement for discharge permits imposes a ceiling on leaching which can successively be lowered by including more crops.

Sure doesn’t look like Kansas! :-)

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Forecasting TDS

Thursday, December 22nd, 2011

February 2012 Article (Early View): “Comparison of the Performance of Statistical Models in Forecasting Monthly Total Dissolved Solids in the Rio Grande,” by Shalamu Abudu1, J. Phillip King, and Zhuping Sheng.

Water quality modeling is a useful tool to evaluate the future state of river water in view of actual pollution loading or different management options. Prediction of the river water quality allows the adequate measurements to be taken to keep the pollutants within the permissible limits. This paper presents the application of autoregressive integrated moving average (ARIMA), transfer function-noise (TFN), and artificial neural networks (ANNs) modeling approaches in forecasting monthly total dissolved solids (TDS) of water in the Rio Grande at El Paso, Texas.

The performances of time series and ANN models in forecasting monthly total dissolved solids (TDS) concentration of the Rio Grande water were compared using one- to three-month-ahead forecasts of the developed models. The results suggested that simple deseasonalized ARIMA models could be used in one- to three-month-ahead TDS forecasting at the study site with a simple, explicit model structure and similar model performance as the TFN and ANN models for better water management in the Basin.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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