Verification of a Methodology for Targeting Brush Control to Maximize Water Yield Through Hydrologic Modeling

Brush control strategies have been implemented for many traditional grasslands that have been impaired by wooded species. However, little information is known concerning what site specific characteristics may be most beneficial for increasing water yields by returning shrub encroached areas to native grasslands. This paper discusses a number of potential targeting criteria for successful brush management and outlines a methodology for testing the role of steep slope, brush density, and shallow soils on successful use of vegetation replacement for increasing water yield

Hydrologic simulation of a neotropical alpine catchment influenced by conductive topsoils in the Ecuadorian Andes

Highly conductive topsoils in neotropical high-elevation grassland-dominated ecosystems, or so-called paramos in the Andean region, influence the local rainfall-runoff processes predominated by saturation-excess overland flow as the primary source of freshwater. The Soil and Water Assessment Tool (SWAT) model has shown limitations when applied to mountainous catchments with highly conductive soils that generate surface runoff as saturation-excess overland flow. In this study, we enhanced SWAT to simulate runoff as saturation-excess overland flow and examined the hydrological responses of an intensively monitored paramo catchment in Ecuador. The model setup considered a detailed representation of the hydro-physical properties of the soils at different depths, including high infiltration and lateral flow rates in the hillslopes and restricted groundwater interactions, a characteristic of the páramo catchments. SWAT reasonably reproduced the daily discharge during dry and wet periods and the cumulative occurrence of high and low flows. The performance metrics NSE, RSR, and PBIAS values during calibration/validation period were 0.86/0.84, 0.31/0.4, and −11.2/-7.58, respectively. The runoff ratio and partitioning of the total runoff into the lateral flow and surface runoff were physically meaningful. More significantly, SWAT was able to simulate saturation-excess overland flow, which is dominant compared to infiltration excess, and it is a distinctive characteristic of páramo catchments. Nevertheless, the model showed limitations in simulating low flows

Verification of a Methodology for Targeting Brush Control to Maximize Water Yield Through Hydrologic Modeling

Brush control strategies have been implemented for many traditional grasslands that have been impaired by wooded species. However, little information is known concerning what site specific characteristics may be most beneficial for increasing water yields by returning shrub encroached areas to native grasslands. This paper discusses a number of potential targeting criteria for successful brush management and outlines a methodology for testing the role of steep slope, brush density, and shallow soils on successful use of vegetation replacement for increasing water yield

Evaluation of potential E. coli transport from on-site sewage facilities in a Texas watershed

Potential E. coli contamination in surface waters from on-site sewage facilities was investigated in the Dickinson Bayou watershed, Texas. This watershed is listed as impaired due to bacteria by the Texas Commission on Environmental Quality. Two water quality monitoring stations, with flow meters and automatic water samplers, were installed in the watershed to assess E. coli concentrations in surface runoff. One monitoring station was installed in a neighborhood that solely used an on-site sewage facility (OSSF) and the second monitoring station, the control site, was installed in a neighborhood connected to a municipal sewage plant. For 16 runoff events at the OSSF site, the combined geometric mean E. coli concentration was 639 colony forming units (CFU)/100milliters while the geometric mean E. coli concentration for 13 runoff events at the control site was 371 CFU/100milliliters. The E. coli concentrations from the 2 sites were not statistically different, suggesting that OSSFs may not be the major cause of bacterial contamination in the Dickinson Bayou watershed. In addition, a bacterial source tracking method was employed, which concluded that a portion of the E. coli from both sites were of human origin. Citation: Morrison D, Karthikeyan R, Munster C, Jacob J, Gentry T. 2017. Evaluation of potential E. coli transport from on-site sewage facilities in a Texas watershed. Texas Water Journal. 8(1):18-28. Available from: https://doi.org/10.21423/twj.v8i1.7041

A Process for Assessing Wooded Plant Cover by Remote Sensing

The ability to map the extent of wooded vegetation cover over large areas using remote sensing is important for managing and assessing rangelands. Currently, applied techniques are inadequate because they 1) do not directly measure the amount of land covered by woody plants and rely on low-resolution images, 2) require considerable training-area data to train a classifier, and 3) describe only a limited number of land cover types. This paper presents an innovative methodology for creating a land-cover map that requires little to no traditional, training-area data collection before classification. The procedure combines both high-resolution aerial photography (resampled to 2.5-m pixels) and lower-resolution satellite imagery (30-m pixels) to produce a detailed and easily producible data set. The resulting data set also categorizes regions into a wide variety of land cover types in addition to differing levels of wooded cover. This new methodology was applied to the Upper Guadalupe River watershed in Texas, which is composed of varying amounts of brush cover between herbaceous range and dense cover. Validation by comparison to aerial imagery demonstrated a 74.4% success rate for all land cover classes. Validation was also performed by ground survey for several brush-covered points and showed a 90.0% success rate. As a result of the ground survey, modifications to the methodology were recommended to reduce classification errors and improve the process.  The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 2020Legacy DOIs that must be preserved: 10.2458/azu_rangelands_v58i2_wilco

Simulating the Hydrologic Impact of Arundo donax Invasion on the Headwaters of the Nueces River in Texas

Arundo donax (hereafter referred to as Arundo), a robust herbaceous plant, has invaded the riparian zones of the Rio Grande River and the rivers of the Texas Hill Country over the last two decades. Arundo was first observed along the Nueces River in central Texas in 1995 by the Nueces River Authority (NRA). It then spread rapidly downstream due to its fast growth rate and availability of streamflow for its consumptive use, and it completely displaced the native vegetation, primarily Panicum virgatum (hereafter referred to as switchgrass) in the riparian zone. It was hypothesized that Arundo reduced streamflows due to higher water use by Arundo when compared to switchgrass. The overall goal of this study was to assess the impacts of Arundo invasion on hydrology of the headwaters of the Nueces River through observed long-term streamflow and precipitation data analysis and simulation modeling with the Soil and Water Assessment Tool (SWAT). The observed data analysis indicated that while there was no significant change in monthly precipitation between the pre-Arundo invasion (1979–1994) and post-Arundo invasion (1995–2010) periods, streamflows changed significantly showing a positive (slightly increasing) trend during the pre-invasion period and a negative (slightly decreasing) trend during the post-invasion periods. The simulated average (1995–2010) annual evapotranspiration of Arundo in the seven Hydrologic Response Units (HRUs) in which Arundo invaded, was higher by 137 mm when compared to switchgrass. The water uptake by Arundo was therefore higher by 7.2% over switchgrass. Higher water uptake by Arundo resulted in a 93 mm higher irrigation (water use from the reach/stream) annually when compared to switchgrass. In addition, the simulated average annual water yield (net amount of water that was generated from the seven Arundo HRUs and contributed to streamflow) under Arundo was less by about 17 mm as compared to switchgrass. In conclusion, model simulations indicated that Arundo invasion in the Nueces River has caused a statistically significant increase in water uptake and reduction in streamflow compared to the native switchgrass, which previously dominated the headwaters

Economic Feasibility of a Mobile Fast Pyrolysis System for Sustainable Bio-crude Oil Production

This paper analyzed the economic feasibility of a mobile bioenergy pyrolysis system using a Monte Carlo simulation model. Pyrolysis transforms any cellulosic materials into i) a bio-oil similar to crude oil ii) a synthesis gas similar to natural gas, and iii) a bio-charcoal substance. The pyrolyzer machine is currently being manufactured and tested with various types of feed-stocks including corn stover and energy sorghum. The economic analysis focused on creating an automated process that integrates a transportation logistics cost optimization model with geo-graphic information system (GIS) data. The geographic data provides possible paths for the mo-bile bioenergy pyrolysis unit as it moves to and from each harvest area, depending on stochastic availability of feedstock (determined by historical crop yields) and distance to oil refineries. The results indicated that there is a low probability of a positive Net Present Value (NPV) with cur-rent economic conditions. In general, the NPV was highest with a stationary scenario and it de-creased with additional moving times. A sensitivity analysis is presented to assess the potential probability of success of a mobile pyrolysis system under alternative oil prices and feedstock costs scenarios

State of the Art of Water for Food Within the Nexus Framework

Purpose of Review: The purpose of this study is to evaluate the state of knowledge regarding water for food within the water-energy-food (WEF) nexus framework. Three topics are considered: improved plant genetics; irrigation technology and practices; and urban agriculture. Recent Findings: Research in plant genetics has sought to understand plant mechanisms that produce higher-yielding crops, identify and map genetic loci regions responsible for desirable plant traits, and introduce new and safe methods of precision plant breeding. In addition, new discoveries in irrigation practices are crucial in sustaining and further increasing yields as a result of improved irrigation water use efficiency through near-real time spatio-temporal monitoring of soil moisture, evapotranspiration, and rainfall. Urban agriculture has been proliferating in recent years, and recent research demonstrates the possibility of non-traditional, urban farming methods to produce food in a water- and land-efficient way. Summary: Opportunities remain to increase water use efficiency and/or decrease water usage throughout the food supply chain. Food producers need to achieve greater value from the water used through enhanced management supported by new technology and guided by scientific findings evolving from multidisciplinary research. To achieve this, constant exchange is needed between regulatory agencies, farmers, food manufacturers, and researchers to ensure all stakeholders are up to date on the issues, policies, technologies, and discoveries related to water and food production sustainability