Archive for October, 2011

Importance of crop yield

Monday, October 31st, 2011

December 2011 article (early view): “Importance of Crop Yield in Calibrating Watershed Water Quality Simulation Tools,” by Sujithkumar Surendran Nair, Kevin W. King, Jonathan D. Witter, Brent L. Sohngen, and Norman R. Fausey

Confidence in a simulation tool’s ability to accurately represent and capture the inherent variability of a watershed is dependent upon high quality input data and subsequent calibration. It is essential that these models allow representation of a wide variety of crops and technology combinations for evaluation and provide reasonable estimates of crop yield and environmental impact of crop production.

In general, calibration and validation of SWAT typically has been evaluated by comparing the simulated surface runoff, and nutrient concentration in runoff, against measured values at a watershed outlet. However, the processes affecting the water and nutrient balance in an agricultural watershed are highly influenced by crop production. The goal of this study was to build upon previous research by further investigating the model’s accuracy in simulating crop biomass and yield, surface flow, nutrient loading, and their interaction in a watershed. The authors propose a calibration approach for SWAT by sequentially integrating hydrology, crop, and nutrient components (in the immediate study only nitrogen).

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

Alaskan groundwater and climate change

Friday, October 28th, 2011

December 2011 article (early view): “The Sensitivity of Northern Groundwater Recharge to Climate Change: A Case Study in Northwest Alaska,” by Hannah M. Clilverd, Daniel M. White, Amy C. Tidwell, and Michael A. Rawlins

The effects of climate change often involve one effect offsetting another. This study is a good example.

Major changes in the arctic and subarctic hydrological cycle have been observed in the last few decades, such as later freeze-up and earlier snowmelt, as well as increased precipitation and runoff. This likely has important consequences for groundwater recharge, which is dependent upon the amount and duration of winter precipitation and spring snowmelt. This study examined the potential impacts of climate change on northern groundwater supplies at a fractured-marble mountain aquifer near Nome, Alaska.

The key factors controlling well water-surface elevations were the length of the winter freeze season and aquifer head recession, the magnitude of winter snow accumulation and spring snowmelt, and the intensity of summer rainfall. Simulations from the Pan-Arctic Water Balance Model (PWBM)  indicate that these hydrologic processes will be altered if the mean annual air temperature increases on the order predicted by ECHAM5 and the associated emissions scenarios. Their study suggests that climatic warming in the subarctic will result in later freeze-up and earlier snowmelt, decreasing the amount of snowfall by the end of the century. Despite a lengthening of the frost-free season and increases in evapotranspiration, substantial increases in annual liquid precipitation are predicted to be sufficient to sustain the groundwater recharge necessary for the maintenance of some northern freshwater supplies.

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

What’s in a name, or map?

Monday, October 24th, 2011

There’s a good editorial in this week’s Nature, “Uncharted Territory,” talking about how territorial disputes are leaking into the pages of science journals.When a paper shows international boundaries, you have to consider whether all concerned parties accept those boundaries. Place names also come into dispute.

My own experience with the Middle East Peace Process taught me the importance people attribute to names and squiggles on maps. Therefore, my first revision to JAWRA’s Instructions for Authors added a section on contested place names:  ”The names of geographic locations and even countries are not always universally accepted. In these cases, JAWRA policy is to use the name preferred by the author. Where necessary to avoid confusion, the editor will add a neutral clarifying note.” I would apply the same policy to boundaries.

Of course, I would never allow an author to use a deliberately provocative name such as the “People’s Republic of Massachusetts” (I’ve heard this in reference to health care.) or the “Lying Capitalist Dogs of …” Authors, even when their intent is not to insult, should always consider how names and boundary representations will be perceived. Sometimes an author has to follow the policy of their country, but good manners always recognize the concerns of others.

Bermuda roof catchments

Monday, October 24th, 2011

December 2011 article (early view): “Rain Water Harvesting in Bermuda,” by Mark P. Rowe

Bermuda roof catchment

This article summarizes some of the findings presented in a 2010 Bermuda Government report entitled ‘‘Bermuda’s Water Supply.’’ A major objective of the report was to evaluate the balance of supply vs. demand and assess the adequacy of a system where the principal supply, namely harvested rain water, is not directly measurable.

With a total population of approximately 64,000, Bermuda has one the highest population densities in the world at 11.4 persons per hectare. Every building in Bermuda must have a roof catchment to collect rain water and an associated water storage tank. The average rate at which rain water is harvested at the typical house with four occupants is, however, insufficient to meet average demand. This article describes some of the design aspects of roof catchments and discusses how roof-supplied water may be augmented.

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

Urban forest effects — snow

Thursday, October 20th, 2011

December 2011 article (early view): “ITREE-HYDRO: SNOW HYDROLOGY UPDATE FOR THE URBAN FOREST HYDROLOGY MODEL,” by Yang Yang, Theodore A. Endreny, and David J. Nowak.

Snow model

This article presents snow hydrology updates made to iTree-Hydro, previously called the Urban Forest Effects—Hydrology model. iTree-Hydro Version 1 was a warm climate model developed by the USDA For- est Service to provide a process-based planning tool with robust water quantity and quality predictions given data limitations common to most urban areas. Cold climate hydrology routines presented in this update to iTree-Hydro include: (1) snow interception to simulate the capture of snow by the vegetation canopy, (2) snow unloading to simulate the release of snow triggered by wind, (3) snowmelt to simulate the solid to liquid phase change using a heat budget, and (4) snow sublimation to simulate the solid to gas phase via evaporation.

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

Colorado River runoff

Wednesday, October 19th, 2011

December 2011 article (early view): “TRENDS IN WESTERN U.S. SNOWPACK AND RELATED UPPER COLORADO RIVER BASIN STREAMFLOW,” by W. Paul Miller and Thomas C. Piechota.

Previous research by the authors hypothesized a change in the character of precipitation (i.e., the frequency and amount of rainfall and snowfall events) throughout the Colorado River Basin. In the current study, 398 snowpack telemetry stations were investigated for trends in cumulative precipitation, snow water equivalent, and precipitation events. Observations of snow water equivalent characteristics were compared to observations in streamflow characteristics. Results indicate that the timing of the last day of the snow season corresponds well to the volume of runoff observed over the traditional peak flow season (April through July); conversely, the timing of the first day of the snow season does not correspond well to the volume of runoff observed over the peak flow season. This is significant to water resource managers and river forecasters, as snowpack characteristics may be indicative of a productive or unproductive runoff season.

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

Dirty turtles

Tuesday, October 18th, 2011

December 2011 article (early view): “Common Snapping Turtles (Chelydra serpentina) as a Source of Fecal Indicator Bacteria in Freshwater Systems,“ Mathew J. Habersack, Theo A. Dillaha, Charles Hagedorn

Maybe we should subtitle the December issue, “Critters that foul your water.” (W.C. Fields had a joke along this line: “Water? Never touch the stuff! Fish …” which I will not finish here.) The culprit in this article is the common snapping turtle.

While conducting research into the bacterial composition of semiaquatic mammal feces, the opportunity presented itself to quantify commonly used pathogen indicator bacteria in the gastrointestinal contents from an ectothermic (cold-blooded) animal, the common snapping turtle. The estimated bacterial loadings from this study demonstrate that the common snapping turtle, if present in sufficient numbers, may contribute significant bacterial loadings to waterways and should be considered when developing bacterial Total Maximum Daily Loads and in other bacterial water quality assessments.

As with birds in the previous posting, turtle feces may not pose the same health risks as human sources, but it is something to consider when sampling and setting standards.

Ewwww! I’m going to think twice before diving into a lake! :-)

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

Dirty birds

Monday, October 17th, 2011

December 2011 article (early view): “Colonies of Cliff Swallows on Highway Bridges: A Source of Escherichia coli in Surface Waters,” by Patrick Sejkora, Mary Jo Kirisits, and Michael Barrett.

Bird droppings from bridges sounds like material for jokes, but the authors report a finding which could explain some unexpected results in your sampling.

The authors’ objective was to determine whether a colony of cliff swallows nesting underneath a bridge would yield a measurable increase in fecal indicator bacteria (specifically Escherichia coli) in the underlying creek. What they found: When the swallows were absent, dry-weather concentrations of E. coli upstream and downstream of the bridge (in Austin, Texas) were below the Texas contact recreation criteria. When the swallows were present, E. coli concentrations increased significantly from upstream (43 most probable number [MPN]/100 ml) to downstream (106 MPN/100 ml) of the bridge. Similar findings were observed for wet weather.

Although the loading of E. coli from cliff swallows nesting under bridges can be significant, the zoonotic potential of the cliff swallow must be examined to determine the risk to human health from contact recreation in waters contaminated with cliff swallow feces.

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