Iowa River Research Articles

Hydroxyl radical formation during ozonation of multiwalled carbon nanotubes: performance optimization and demonstration of a reactive CNT filter.

We explored factors influencing hydroxyl radical (•OH) formation during ozonation of multiwalled carbon nanotubes (MWCNTs) and assessed this system's viability as a next-generation advanced oxidation process (AOP). Using standard reactivity metrics for ozone-based AOPs (RCT values), MWCNTs promoted •OH formation during ozonation to levels exceeding ozone (both alone and with activated carbon) and equivalent to ozone with hydrogen peroxide. MWCNTs oxidized with nitric acid exhibited vastly greater rates of ozone consumption and •OH formation relative to as-received MWCNTs. While some of this enhancement reflects their greater suspension stability, a strong correlation between RCT values and surface oxygen concentrations from X-ray photoelectron spectroscopy suggests that surface sites generated during MWCNT oxidation promote •OH exposure. Removal of several ozone-recalcitrant species [para-chlorobenzoic acid (p-CBA), atrazine, DEET, and ibuprofen] was not significantly inhibited in the presence of radical scavengers (humic acid, carbonate), in complex aquatic matrices (Iowa River water) and after 12 h of continuous exposure of MWCNTs to concentrated ozone solutions. As a proof-of-concept, oxidized MWCNTs deposited on a ceramic membrane chemically oxidized p-CBA in a flow through system, with removal increasing with influent ozone concentration and mass of deposited MWCNTs (in mg/cm2). This hybrid membrane platform, which integrates adsorption, oxidation, and filtration via an immobilized MWCNT layer, may serve as the basis for future novel nanomaterial-enabled technologies, although long-term performance trials under representative treatment scenarios remain necessary.

Recession analysis across scales: The impact of both random and nonrandom spatial variability on aggregated hydrologic response

Summary Recession analysis across scales can provide insight into the spatial aggregation of hydrologic processes. Accordingly, we analyzed individual late-time recession curves from 25 nested USGS stream gauges over a period of ∼150 days with negligible precipitation during the 2012–2013 North American drought. These gauges are located in the Iowa and Cedar River basins and drain areas ranging from ∼70 to 17,000 km2. Our data analyses show that these late-time recession processes can be represented by a linear reservoir model with a constant recession time scale of about 34 days, indicating linear and homogeneous recession behaviors at the large scales investigated. However, others have shown that the early-time recession process becomes more nonlinear as spatial scale and, thus, spatial variability increases. We developed a distributed drainage model as a diagnostic tool to understand these seemingly contradictory recession characteristics at multiple spatial scales and different stages. With a hierarchical description of the recession variability at the hillslope scale, our model can simultaneously produce the increasing nonlinear early-time and the linear and homogenous late-time recession behaviors at larger scales. The hierarchical representation classifies hillslopes according to the Strahler orders of the stream links into which they drain. We postulate that a larger difference in recession behaviors will occur between hillslopes from different orders than between those from the same order. Overall, this study shows how the spatial randomness and nonrandomness of small-scale process variability control the hydrologic responses at larger scales and suggests a combined (nonrandom–random) representation of watersheds for aggregating hydrologic processes.

The integrated effects of climate and hydrologic uncertainty on future flood risk assessments

AbstractThis work examines future flood risk within the context of integrated climate and hydrologic modelling uncertainty. The research questions investigated are (1) whether hydrologic uncertainties are a significant source of uncertainty relative to other sources such as climate variability and change and (2) whether a statistical characterization of uncertainty from a lumped, conceptual hydrologic model is sufficient to account for hydrologic uncertainties in the modelling process. To investigate these questions, an ensemble of climate simulations are propagated through hydrologic models and then through a reservoir simulation model to delimit the range of flood protection under a wide array of climate conditions. Uncertainty in mean climate changes and internal climate variability are framed using a risk‐based methodology and are explored using a stochastic weather generator. To account for hydrologic uncertainty, two hydrologic models are considered, a conceptual, lumped parameter model and a distributed, physically based model. In the conceptual model, parameter and residual error uncertainties are quantified and propagated through the analysis using a Bayesian modelling framework. The approach is demonstrated in a case study for the Coralville Dam on the Iowa River, where recent, intense flooding has raised questions about potential impacts of climate change on flood protection adequacy. Results indicate that the uncertainty surrounding future flood risk from hydrologic modelling and internal climate variability can be of the same order of magnitude as climate change. Furthermore, statistical uncertainty in the conceptual hydrological model can capture the primary structural differences that emerge in flood damage estimates between the two hydrologic models. Copyright © 2014 John Wiley & Sons, Ltd.

Anthropogenic Disturbance and Environmental Associations with Fish Assemblage Structure in Two Nonwadeable Rivers

AbstractNonwadeable rivers are unique ecosystems that support high levels of aquatic biodiversity, yet they have been greatly altered by human activities. Although riverine fish assemblages have been studied in the past, we still have an incomplete understanding of how fish assemblages respond to both natural and anthropogenic influences in large rivers. The purpose of this study was to evaluate associations between fish assemblage structure and reach‐scale habitat, dam, and watershed land use characteristics. In the summers of 2011 and 2012, comprehensive fish and environmental data were collected from 33 reaches in the Iowa and Cedar rivers of eastern‐central Iowa. Canonical correspondence analysis (CCA) was used to evaluate environmental relationships with species relative abundance, functional trait abundance (e.g. catch rate of tolerant species), and functional trait composition (e.g. percentage of tolerant species). On the basis of partial CCAs, reach‐scale habitat, dam characteristics, and watershed land use features explained 25.0–81.1%, 6.2–25.1%, and 5.8–47.2% of fish assemblage variation, respectively. Although reach‐scale, dam, and land use factors contributed to overall assemblage structure, the majority of fish assemblage variation was constrained by reach‐scale habitat factors. Specifically, mean annual discharge was consistently selected in nine of the 11 CCA models and accounted for the majority of explained fish assemblage variance by reach‐scale habitat. This study provides important insight on the influence of anthropogenic disturbances across multiple spatial scales on fish assemblages in large river systems. Copyright © 2014 John Wiley & Sons, Ltd.

The impact of gender on agricultural conservation knowledge and attitudes in an Iowa watershed

Female agricultural land ownership and operatorship are on the rise in Iowa and across the nation, but little research exists that explores agricultural conservation outreach to women and gendered differences in conservation knowledge and attitudes. The authors surveyed all agricultural landowners and operators in the Clear Creek Watershed in eastern Iowa about conservation knowledge and attitudes, as well as preferred sources of information about conservation. Clear Creek is a high-visibility watershed for conservation outreach for several reasons, including its long-standing watershed stakeholder council and its connection to the impaired Iowa River. Analysis of the survey results demonstrated that female respondents had significantly lower levels of knowledge about best management practices and significantly more positive attitudes towards conservation and collaboration than men. Meanwhile, women looked to the same sources for conservation information as male respondents, including neighbors, friends, and conservation agencies like the Natural Resources Conservation Service, Cooperative Extension, and the Farm Service Agency. These gendered results have significant consequences for the future of agricultural conservation practice and policy and for the subsequent health of the nation's soils and waterways. While lacking in knowledge about specific conservation practices, female respondents valued conservation practices, looked to government agencies for information about conservation, and expressed interest in collaborating with government entities for conservation on their land. Agricultural conservation practitioners can use these findings to tailor outreach efforts that will more effectively reach the nation's female landowners and operators.

Historical Changes in Fish Assemblage Structure in Midwestern Nonwadeable Rivers

Historical change in fish assemblage structure was evaluated in the mainstems of the Des Moines, Iowa, Cedar, Wapsipinicon, and Maquoketa rivers, in Iowa. Fish occurrence data were compared in each river between historical and recent time periods to characterize temporal changes among 126 species distributions and assess spatiotemporal patterns in faunal similarity. A resampling procedure was used to estimate species occurrences in rivers during each assessment period and changes in species occurrence were summarized. Spatiotemporal shifts in species composition were analyzed at the river and river section scale using cluster analysis, pairwise Jaccard's dissimilarities, and analysis of multivariate beta dispersion. The majority of species exhibited either increases or declines in distribution in all rivers with the exception of several “unknown” or inconclusive trends exhibited by species in the Maquoketa River. Cluster analysis identified temporal patterns of similarity among fish assemblages in the Des Moines, Cedar, and Iowa rivers within the historical and recent assessment period indicating a significant change in species composition. Prominent declines of backwater species with phytophilic spawning strategies contributed to assemblage changes occurring across river systems.

Effectiveness of natural riparian buffers to reduce subsurface nutrient losses to incised streams

Perennial vegetation borders many incised, perennial streams and rivers in southern Iowa and is assumed to provide a natural riparian buffer against subsurface nutrient losses from shallow groundwater. Questions remain about the effectiveness of these systems near incised channels that cut through nutrient-rich Holocene alluvium underlying the riparian corridors. In this study, riparian groundwater nutrient concentrations were evaluated near an incised stream under four perennial land cover types common to southern Iowa with the objectives to assess how groundwater quality differed by i) distance away from an incised stream and ii) perennial land cover type. Groundwater samples were collected from riparian wells installed 1m, 20m and 40m from an incised channel under four replicated land covers (cool season grass, warm season grass, woods, pasture) on six occasions across the growing season. Results indicate that channel incision lowers water tables in the near-stream zone and maintains more aerobic conditions but did not result in enhanced nitrogen mineralization or leaching to groundwater. Average concentrations of nitrate–nitrogen, phosphorus and dissolved organic carbon were 0.3mg/l, 0.2mg/l and 6mg/l, respectively, with variations due mainly to land cover type and geomorphology. Study results suggest that nutrient losses from perennial buffers in the region do not greatly impact regional water N and P loads although average concentrations in riparian groundwater may exceed proposed stream nutrient criteria.

Nitrate Concentration Trends in Iowa's Rivers, 1998 to 2012: What Challenges Await Nutrient Reduction Initiatives?

Nitrate-nitrogen (NO-N) concentrations threaten water supplies and contribute to impairments of surface water resources. In this study, we analyzed concentration trends at 60 ambient river monitoring sites in Iowa for the years 1998 to 2012 to assess the presence of linear trends in the NO-N concentration data using a time-series method that accounted for temporal correlation and combined the trend information from individual sites into an assessment of the state-wide rate of change in river NO-N concentrations. Forty-six of the sites had sufficient records for trend analysis. Study results indicated that 37 out of 46 sites (80%) did not have statistically significant trends over the monitoring period ( > 0.1). Six monitoring sites in western Iowa had statistically significant increasing trends ( < 0.05), and three additional sites located in western and southern Iowa showed nominally significant increasing trends ( < 0.1). The rate of statistically significant increases ranged from 0.15 to 0.33 mg L yr. Aggregated across the state, the overall trend of NO-N concentrations in Iowa rivers is increasing, with an average and median rate of 0.05 and 0.03 mg L yr, respectively. Increasing concentration is likely associated with increasing trends in fertilizer sales and animal production, but better tracking is needed to establish a definitive relation. Reducing NO-N concentrations using conservation practices is a major focus of the recently proposed Iowa Nutrient Reduction Strategy, and our study provides an important milestone preceding implementation of the strategy.

Improvement of the R-SWAT-FME framework to support multiple variables and multi-objective functions

Application of numerical models is a common practice in the environmental field for investigation and prediction of natural and anthropogenic processes. However, process knowledge, parameter identifiability, sensitivity, and uncertainty analyses are still a challenge for large and complex mathematical models such as the hydrological/water quality model, Soil and Water Assessment Tool (SWAT). In this study, the previously developed R program language-SWAT-Flexible Modeling Environment (R-SWAT-FME) was improved to support multiple model variables and objectives at multiple time steps (i.e., daily, monthly, and annually). This expansion is significant because there is usually more than one variable (e.g., water, nutrients, and pesticides) of interest for environmental models like SWAT. To further facilitate its easy use, we also simplified its application requirements without compromising its merits, such as the user-friendly interface. To evaluate the performance of the improved framework, we used a case study focusing on both streamflow and nitrate nitrogen in the Upper Iowa River Basin (above Marengo) in the United States. Results indicated that the R-SWAT-FME performs well and is comparable to the built-in auto-calibration tool in multi-objective model calibration. Overall, the enhanced R-SWAT-FME can be useful for the SWAT community, and the methods we used can also be valuable for wrapping potential R packages with other environmental models.

FISH ASSEMBLAGE RELATIONSHIPS WITH PHYSICAL CHARACTERISTICS AND PRESENCE OF DAMS IN THREE EASTERN IOWA RIVERS

ABSTRACTFish assemblages in rivers of the Midwestern United States are an important component of the region's natural resources and biodiversity. We characterized the physical environment and presence of dams in a series of reaches in three eastern Iowa rivers tributary to the Mississippi River and related these characteristics to the fish assemblages present. Some physical characteristics were similar among the 12 study reaches, whereas others differed substantially. We found a total of 68 species across the 12 study reaches; 56 in the Turkey River, 51 in the Maquoketa River and 50 in the Wapsipinicon River. Seventeen species could be described as ‘downstream‐distributed’; 15 being found only in the lowest reach of one or more rivers and the other two being found only in the lowest reaches or two or more contiguous reaches including the lowest reach. Two species could be described as ‘upstream‐distributed’, being found only in an uppermost reach. Non‐metric multidimensional scaling ordination illustrated similarities among reaches, and five physical variables were significantly correlated with assemblage similarities. Catchment area and number of dams between reaches and the Mississippi River were strongly correlated with assemblage similarities, but the directions of their effects were opposite. Catchment area and number of dams were confounded. The collective evidence to date suggests that the pervasiveness of dams on rivers significantly alters fish assemblages, making underlying patterns of species change and relationships with naturally varying and human‐influenced physical characteristics along a river's course difficult to discern. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Three Dimensional Numerical Modeling of Flow and Pollutant Transport in a Flooding Area of 2008 US Midwest Flood

This paper presents the development and application of a three-dimensional numerical model for simulating the flow field and pollutant transport in a flood zone near the confluence of the Mississippi River and Iowa River during the US Midwest Flood in 2008. Due to a prolonged precipitation event, a levee along the Iowa River just upstream of Oakville, Iowa broke, and the small town was completely flooded for a couple of weeks. During this period, the high water level in the flood zone reached about 2.5 metersabove the ground, and wind was the major force for the flow circulation. It was observed that some pollutants were leaked from the residential and farming facilities and transported into the flood zone. Leaking of pollutants from these facilities was reported by different news media during the flood and was identified using high resolution satellite imagery. The developed 3D numerical model was first validated using experimental measurements, and then applied to the flood inundated zone in Oakville for simulating the unsteady hydrodynamics and pollutant transport. The simulated pollutant distributions were generally in good agreement with the observed data obtained from satellite imagery.

Eleven‐Year Trend in Acetanilide Pesticide Degradates in the Iowa River, Iowa

Trends in concentration and loads of acetochlor, alachlor, and metolachlor and their ethanasulfonic (ESA) and oxanilic (OXA) acid degradates were studied from 1996 through 2006 in the main stem of the Iowa River, Iowa and in the South Fork Iowa River, a small tributary near the headwaters of the Iowa River. Concentration trends were determined using the parametric regression model SEAWAVE-Q, which accounts for seasonal and flow-related variability. Daily estimated concentrations generated from the model were used with daily streamflow to calculate daily and yearly loads. Acetochlor, alachlor, metolachlor, and their ESA and OXA degradates were generally present in >50% of the samples collected from both sites throughout the study. Their concentrations generally decreased from 1996 through 2006, although the rate of decrease was slower after 2001. Concentrations of the ESA and OXA degradates decreased from 3 to about 23% yr. The concentration trend was related to the decreasing use of these compounds during the study period. Decreasing concentrations and constant runoff resulted in an average reduction of 10 to >3000 kg per year of alachlor and metolachlor ESA and OXA degradates being transported out of the Iowa River watershed. Transport of acetochlor and metolachlor parent compounds and their degradates from the Iowa River watershed ranged from <1% to about 6% of the annual application. These trends were related to the decreasing use of these compounds during the study period, but the year-to-year variability cannot explain changes in loads based on herbicide use alone. The trends were also affected by the timing and amount of precipitation. As expected, increased amounts of water moving through the watershed moved a greater percentage of the applied herbicides, especially the relatively soluble degradates, from the soils into the rivers through surface runoff, shallow groundwater inflow, and subsurface drainage.

Transformation of forest soils in Iowa (United States) under the impact of long-term agricultural development

The evolution of automorphic cultivated soils of the Fayette series (the order of Alfisols)—close analogues of gray forest soils in the European part of Russia—was studied by the method of agrosoil chronosequences in the lower reaches of the Iowa River. It was found that the old-arable soils are characterized by an increase in the thickness of humus horizons and better aggregation; they are subjected to active biogenic turbation by rodents; some alkalization of the soil reaction and an increase in the sum of exchangeable bases also take place. These features are developed against the background of active eluvial-illuvial differentiation and gleyzation of the soil profiles under conditions of a relatively wet climate typical of the ecotone between the zones of prairies and broadleaved forests in the northeast Central Plains of the United States.

Modeling of land use and reservoir effects on nonpoint source pollution in a highly agricultural basin

Nonpoint source (NPS) pollution is tightly linked to land use activities that determine the sources and magnitudes of pollutant loadings to stream water. The pollutant loads may also be alleviated within reservoirs because of the physical interception resulting from changed hydrological regimes and other biochemical processes. It is important but challenging to assess the NPS pollution processes with human effects due to the measurement limitations. The objective of this study is to evaluate the effects of human activities such as land uses and reservoir operation on the hydrological and NPS pollution processes in a highly agricultural area-the Iowa River Basin-using the Soil and Water Assessment Tool (SWAT). The evaluation of model performance at multiple sites reveals that SWAT can consistently simulate the daily streamflow, and monthly/annual sediment and nutrient loads (nitrate nitrogen and mineral phosphorus) in the basin. We also used the calibrated model to estimate the trap efficiencies of sediment (∼78%) and nutrients (∼30%) in the Coralville Reservoir within the basin. These non-negligible effects emphasize the significance of incorporating the sediment and nutrient removal mechanisms into watershed system studies. The spatial quantification of the critical NPS pollution loads can help identify hot-spot areas that are likely locations for the best management practices.

Impacts of biofuels production alternatives on water quantity and quality in the Iowa River Basin

Corn stover as well as perennial grasses like switchgrass (Panicum virgatum) and miscanthus are being considered as candidates for the second generation biofuel feedstocks. However, the challenges to biofuel development are its effects on the environment, especially water quality. This study evaluates the long-term impacts of biofuel production alternatives (e.g., elevated corn stover removal rates and the potential land cover change) on an ecosystem with a focus on biomass production, soil erosion, water quantity and quality, and soil nitrate nitrogen concentration at the watershed scale. The Soil and Water Assessment Tool (SWAT) was modified for setting land cover change scenarios and applied to the Iowa River Basin (a tributary of the Upper Mississippi River Basin). Results show that biomass production can be sustained with an increased stover removal rate as long as the crop demand for nutrients is met with appropriate fertilization. Although a drastic increase (4.7–70.6%) in sediment yield due to erosion and a slight decrease (1.2–3.2%) in water yield were estimated with the stover removal rate ranging between 40% and 100%, the nitrate nitrogen load declined about 6–10.1%. In comparison to growing corn, growing either switchgrass or miscanthus can reduce sediment erosion greatly. However, land cover changes from native grass to switchgrass or miscanthus would lead to a decrease in water yield and an increase in nitrate nitrogen load. In contrast to growing switchgrass, growing miscanthus is more productive in generating biomass, but its higher water demand may reduce water availability in the study area.

A Soil Quality Assessment within the Iowa River South Fork Watershed

A Soil Quality Assessment within the Iowa River South Fork Watershed

Trophic ecology and gill raker morphology of seven catostomid species in Iowa rivers

Summary Understanding the trophic ecology of closely-related species is important for providing insight on inter-specific competition and resource partitioning. Although catostomids often dominate fish assemblages in lotic systems, little research has been conducted on their ecology. This study was developed to provide information on the trophic ecology of catostomids in several Iowa rivers. Food habits, diet overlap, and gill raker morphology were examined for highfin carpsucker Carpiodes velifer, quillback C. cyprinus, river carpsucker C. carpio, golden redhorse Moxostoma erythrurum, shorthead redhorse M. macrolepidotum, silver redhorse M. anisurum, and northern hogsucker Hypentelium nigricans sampled from four Iowa rivers (2009). Diet overlap among all species was calculated with Morista’s index (C). Food habit niche width was quantified with Levin’s index (B) and similarity in gill raker morphology was compared with analysis of covariance. Values from Morista’s index suggested significant overlap in the diets of highfin carpsucker and river carpsucker (C = 0.81), quillback and river carpsucker (C = 0.66), and shorthead redhorse and silver redhorse (C = 0.67). Levin’s index indicated that golden redhorse (B = 0.32), quillback (B = 0.53), and river carpsucker (B = 0.41) had the most generalized feeding strategies as their food niche widths were substantially wider than the other species. Gill raker length and spacing were positively correlated with the standard length of the fish for all species (gill raker length: r2 = 0.67–0.88, P ≤ 0.01; gill raker spacing: r2 = 0.63–0.73, P ≤ 0.01). Slopes of regression of gill raker length and spacing to standard lengths were significantly (P ≤ 0.05) different among species, indicating that rates of change in gill raker morphology with body length varied among species. Differences in gill raker morphology likely allow catostomids to partition resources and reduce competitive interactions.

POPULATION DEMOGRAPHICS OF CATOSTOMIDS IN LARGE RIVER ECOSYSTEMS: EFFECTS OF DISCHARGE AND TEMPERATURE ON RECRUITMENT DYNAMICS AND GROWTH

ABSTRACTCatostomids are among the most widespread and ecologically important groups of fishes in North America, particularly in large river systems. Despite their importance, little information is available on their population demographics and even less is known about factors influencing their population dynamics. The objectives of this study were to describe annual mortality, recruitment variation, and growth of eight catostomid species, and to evaluate the effects of discharge and temperature on year‐class strength and growth in Iowa rivers. Catostomids were sampled from 3‐km reaches in four nonwadable rivers during June–August 2009. Northern hogsucker, Hypentelium nigricans, golden redhorse, Moxostoma erythrurum, and shorthead redhorse, M. macrolepidotum, typically lived 6–8 years, had very stable recruitment, and had high total annual mortality (i.e., 40–60%). Golden redhorse exhibited the fastest growth of all species. Growth of northern hogsucker and shorthead redhorse was intermediate to the other catostomids. Highfin carpsucker, Carpiodes velifer, quillback, Carpiodes cyprinus, and white sucker, Catostomus commersonii, had high growth rates, low mortality (i.e., 25–30%), and relatively stable recruitment. River carpsucker, Carpiodes carpio, and silver redhorse, M. anisurum, had higher maximum ages (up to age 11), slower growth, lower total annual mortality (20–25%), and higher recruitment variability than the other species. Neither discharge nor temperature was strongly related to recruitment of catostomids. In contrast, several interesting patterns were observed with regard to growth. Species (e.g., carpsuckers, Carpiodes spp.) that typically consume prey items most common in fine substrates (e.g., chironomids) had higher growth rates in reaches dominated by sand and silt substrate. Species (e.g., northern hogsucker) that consume prey associated with large substrates (e.g., plecopterans) had much faster growth in reaches with a high proportion of rocky substrates. Temperature was weakly related to growth of catostomids; however, discharge explained a substantial amount of the variation in growth of nearly all species. Results of this study provide important information on the autecology of catostomids that can be used for comparison among species and systems. These data also suggest that connection of rivers with their floodplain is an important feature for catostomids in temperate river systems. Published in 2011 by John Wiley &amp; Sons, Ltd.

Treatments of Precipitation Inputs to Hydrologic Models

Hydrologic models are used to assess many water resource problems, from agricultural use and water quality to engineering issues. This study shows how the combination of rain gauges (accurate at a point) and NEXRAD precipitation data (covering a wide area) can provide accurate, timely rainfall data that can drive the Soil and Water Assessment Tool (SWAT) model, which provides a more reliable tool for producers and policy-makers alike. The treatment of rainfall data was tested in the South Fork of the Iowa River, which covers about 788 km2 (194,720 ac) and is one of 15 benchmark watersheds of the USDA Conservation Effects Assessment Project (CEAP). The results show significant improvement in model predictions in which rainfall data were correctly modified. Gauge records with values for trace events performed better as data sources than records in which trace events were given zero value, even though the mean annual rainfall differed by <25 mm. The combination of rain gauge and NEXRAD data provided superior results even when the watershed included a sufficient spatial distribution of rain gauges. Of the six methods used to adjust gauge and NEXRAD data, inverse distance weighting or kriging with external drift predicted streamflow among the four gauges was the best among those tested. In the absence of rain gauge data, the simple adjustment of the NEXRAD estimates to match total rainfall amounts in the region resulted in adequate streamflow estimates. This finding is important because uncorrected NEXRAD precipitation values, although only 15% below annual precipitation values, resulted in a greater than 50% difference in streamflow estimates. The choice of rainfall treatment should be considered carefully to provide accurate model predictions.

Considerations on direct stream flow measurements using video imagery: Outlook and research needs

The paper presents measurements acquired with Large-Scale Particle Image Velocimetry (LSPIV) during normal flows and floods in the Iowa River (U.S.A). For normal flows, comparison is made with measurements obtained with Acoustic Doppler Current Profilers (ADCP) in order to test LSPIV’s performance and to address concerns potentially affecting the accuracy of the measurements. The historic flood of the Iowa River during the summer of 2008 was captured for testing LSPIV capabilities during extreme flows. Lacking alternative measurements during the flood, the LSPIV measurements are compared to the rating curve extrapolated for high flows using a one-to-one discharge–stage relationship. The comparison reveals limitations of the single-values rating curve for providing discharge estimates during high flows. Finally, the paper summarizes lessons learned during these and previous LSPIV studies with the intent to chart the research needed to enhance this promising non-intrusive field measurement technique.