Driftless Area Research Articles

COVID-19 Pandemic Effects on Angler Effort and a Brown Trout Population in a Driftless Area Stream in Southeast Minnesota

Abstract Early opinions of the COVID-19 pandemic included equivocal notions of whether the pandemic would result in more or less angler effort and harvest in recreational fisheries. Early papers also suggested using changes in angling license sales to infer changes in angler effort but expressed concern about adequate assessment of pandemic effects on fisheries because of interruptions to routine assessment programs. To assess pandemic effects on angler effort at a stream trout fishery, a trail camera was installed, immediately prior to implementation of a statewide stay-at-home order, at a representative stream trout angling site that is part of a long-term fish monitoring program. The trail camera was deployed through the trout harvest angling season from the peak pandemic year of 2020 through cessation of most restrictions in 2022. Statewide sales of angling licenses and trout stamps were assessed through this time to compare with angler effort measured with the trail camera. Annual trout population assessments were examined for pandemic effects in conjunction with angler effort. Anglers were present on 84% of days in 2020, 66% in 2021 and 69% in 2022. Following the pandemic peak of 603 angler-hours in 2020, angler-hours declined by -23% between 2020 and 2021, and by -16% between 2020 and 2022; whereas statewide sales of licenses and trout stamps only declined by -4% between 2020 and 2021 and -11% between 2020 and 2022, suggesting more angler pressure at the study site than could be inferred by changes in license or trout stamp sales. Higher pressure during the pandemic was due in part to more anglers younger than 20 years old. Despite higher angler pressure in 2020, there was no long-term effect on the Brown Trout population, as adult abundance in 2021 and 2022 exceeded abundance in every year from 2017 to 2020. These data add to a limited number of similar field-based pandemic studies coupling changes in angler use with fish population responses and should provide further insight into the broader assessment of COVID-19 pandemic effects.

The LTAR Integrated Common Experiment at Upper Mississippi River Basin-Platteville.

Alternative agronomic practices are needed to address the various climatic, agronomic, edaphic, and water quality related challenges faced by the dairy farmers of the Driftless Area (DA) in the Upper Mississippi River Basin (UMRB). These practices should be innovative in nature, inclusive of regional stakeholders, and sustainable to meet the future food and climate related challenges of Wisconsin agriculture. Here, we outline our Integrated (grazing and cropland) Long-Term Agroecosystem Research Common Experiment at the University of Wisconsin-Platteville Pioneer Farm (UW-P PF) in the UMRB and describe our collaboration in this USDA network. In this field-scale experiment, we are comparing the conventional dairy production system common to this region (i.e., corn-on-corn [Zea mays L.] for 4 years, followed by alfalfa [Medicago sativa L.] for 3 years, with no cover crops) with two alternative dairy production systems-(1) soil health management with no-till, cover crops, and application of a novel manure-based nutrient-rich stable product, and (2) management intensive grazing-and rotational grazing on pastures established with diverse forage-legume mix. Meteorological, edaphic, hydrologic, and agronomic data are collected and analyzed at regular frequencies. Going forward, the experiment will continue as a form of stakeholder-driven adaptive research and receive evaluation on a regular basis to determine whether any changes are required to address the "real-world" challenges faced by the farmers in the Midwest.

Brook Trout population response to Brown Trout removal by electrofishing in a Wisconsin Driftless Area stream

Brook Trout population response to Brown Trout removal by electrofishing in a Wisconsin Driftless Area stream

A large phylo-floristic study on the present and future assembly of the Wisconsin flora – An area unique in North America

With 1.4 million specimens the Wisconsin State Herbarium (WIS) is one of the largest in the Americas and Wisconsin offers botanists a unique opportunity to study species representing a confluence of global biomes. The state harbors >2640 species of vascular plants which have been sequenced for the two-gene plant DNA barcode to reconstruct a community phylogeny. At the same time >300’000 georeferenced specimens were used with bioclimatic and soil data to produce species distribution models for the flora, then subsequently aggregated to determine current and future patterns of species richness and phylogenetic diversity. Among the many surprising results uncovered are predictions that whereas species richness will increase as c. 850 taxa move into the state, c. 242 species will become extirpated by 2070. These most vulnerable species will not be affected at random. Furthermore, models suggest that Wisconsin’s projected climate will be unsuitable for most species to be able to retain their present distributions; only 65 % will be able to retain more than half of their current distributions. However, the state’s well known unglaciated Driftless Area may be able to serve as an Anthropocene refugium better than anywhere else in the region and should be targeted for increased land conservation.

Benthic macroinvertebrate community structure in nutrient‐rich, spring‐fed streams recently invaded by non‐native New Zealand mud snails

Abstract Ecological roles of non‐native species can vary over space and time due to abiotic factors and characteristics of the invaded communities. For instance, nutrient availability, temperature, and flow regime can influence invasion outcomes in freshwaters. This variability makes it challenging to predict non‐native species' effects in newly introduced areas. New Zealand mud snails (Potamopyrgus antipodarum; NZMS) are among the most widespread aquatic invasive species globally and have recently been detected in highly productive, spring‐fed streams in the upper mid‐west U.S.A. that are important trout fisheries. We hypothesised that the nutrient‐rich, thermally stable groundwater‐fed streams would provide favourable conditions for NZMS populations, potentially amplifying their effects on native communities. We surveyed benthic macroinvertebrate community structure at 10 streams representing a gradient of NZMS densities in the Driftless Area of southern Wisconsin. At five of the streams, we quantified temporal variation in NZMS and other benthic macroinvertebrates over three seasons. NZMS populations varied considerably across sites and over time, ranging from a few hundred to over 70,000 snails/m2. NZMS numerically represented as much as 97% of the invertebrate community at the highest density sites. At two sites, NZMS increased in population density by 50‐fold and 22‐fold over the survey duration, while at other sites their densities were relatively constant. Based on a principal components analysis summarising stream environmental variables, NZMS densities were negatively associated with stream discharge and positively associated with nitrogen and phosphorus concentrations. The total density and biomass of all benthic invertebrates, and Ephemeroptera and Amphipoda in particular, were negatively associated with NZMS density and biomass. Based on multivariate analyses, overall benthic community composition differed based on NZMS invasion status, as well as across seasons. These results suggest that the environments of southern Wisconsin spring‐fed streams provide favourable conditions for NZMS populations, allowing them to dominate some benthic communities. NZMS effects are likely to vary strongly across streams and over time within streams, highlighting the importance of future work to mechanistically test biotic and abiotic factors influencing their abundance.

Endophytic Fungal Infection of Meadow Fescue in the Driftless Area of the Upper Mississippi River Valley: Impacts on Agronomic Fitness

Meadow fescue, Schedonorus pratensis (Huds.) P. Beauv., has recently been discovered as a common but previously unknown pasture grass in the Driftless Area of the upper Mississippi River Valley, USA. Preliminary data also indicated that many meadow fescue pastures were infected with an endophytic fungus, Epichloë uncinata (W. Gams, Petrini & D. Schmidt) Leuchtm. & Schardl. Therefore, the objective of this study was to determine if the endophyte impacts agronomic fitness of the host meadow fescue. Meadow fescue plants from eight farm sites were intensively sampled, and endophyte infection levels were determined to range from 82 to 95%. Paired endophyte-infected (E+) and endophyte-free (E−) meadow fescue subpopulations from each collection site were then created, and were subsequently compared for greenhouse and field drought tolerance, forage mass, and persistence under frequent defoliation. There was no impact of the endophyte under a wide range of drought conditions for either greenhouse or field studies. Furthermore, there was a small forage-mass-enhancement effect in the E+ subpopulation for only one of the eight collection sites. The only consistent effect was an average of 9% increased ground cover (persistence) in endophyte-infected meadow fescue under frequent defoliation. As per other studies, enhanced root growth, fungal-disease resistance, and/or reduced insect feeding could be mechanisms for this increased survivorship. We conclude that the meadow fescue endophytes present in the Driftless Area do not help protect their host from drought or provide any consistent forage-growth enhancement; however, we found evidence that the endophyte provides some protection against frequent defoliation at low residual sward heights.

What Was the Norm Is No Longer the Norm: Capturing Socio-Ecological Histories of Flood Resilience in Wisconsin’s Driftless Area through Archival News Analysis

Wisconsin’s Driftless Area, an unglaciated region defined by steep river valley systems, has been plagued by chronic flooding in part due to Euro-American agricultural practices and anthropogenic climate change. The region, which has played a central role in environmental knowledge production, has a storied history of resilience practices and flood experience. To capture histories of Driftless Area flood experience and underlying socio-ecological dynamics, we performed a qualitative analysis of regional news archives from 1866 to present on flood trends, experiences, and responses. Our analysis identified hazard response trends mediated by socio-ecological factors including crisis-induced windows of opportunity for change, conflicts over structural and nonstructural responses to flooding, and psychological dimensions of environmental crises. Finally, our analysis noted the key role of community flood knowledge in producing shifts toward enhanced resilience, suggesting the need for empowering flood response planning at the community scale.

Grass versus trees: A proxy debate for deeper anxieties about competing stream worlds

Stream restoration has become an increasingly important focus in southwestern Wisconsin's Driftless Area, an unglaciated, hilly pocket of the Upper Mississippi River Basin rich in groundwater-driven coldwater streams, recreationally important trout species, and agricultural communities. Climate change is driving a major increase in precipitation and flooding across this rural and often under-resourced region, effects complicated by the ongoing legacies of white settlement and the changes it wrought to area streams, including the burial of floodplains in sediment displaced off area hillslopes. As managers work to consider how to “restore” Driftless streams, riparian vegetation—grass versus trees—has become a central and surprisingly controversial node. Current stream restoration practice typically includes the removal of riparian trees, though that practice has come under increasing criticism. Grounded in more than 5 years of qualitative and biophysical fieldwork in the region, we build from interviews gathered with 18 Driftless Area stream restoration managers from 2018 to 2020 to point to the ways that managers leverage arguments about erosion, flooding, habitat, and angler access, among other things, in service of grass and trees. Indexing the surface flows and underflows of this restoration debate, we introduce the rhetorical concept of the proxy debate to argue that debates about grass versus trees are tethered to competing perspectives on scale, temporality, and dynamism, surficial distractions from much deeper anxieties about what a stream is and should be. We turn to the ways that these distractions serve to further distance the stream restoration enterprise from acknowledging the ongoing human and hydrologic legacies of settler colonialism, and we close by suggesting that careful attention to rhetorical power—both to what arguments say and do, and to what they elide—offers a tentative first step toward restoring lands and relations by questioning what is taken for granted and what lies beneath.

Landscape Performance: Farmer Interactions across Spatial Scales

Agricultural lands in the north-central United States represent some of the most uniform and non-sustainable landscapes in human history. The conformity in land-use practices reflects a broad social agreement, albeit unspoken, of having an influence on agricultural practices and is referred to as a normative landscape. Implementing conservation agricultural practices requires engaging such social agreements in ways that question and disrupt them. By using a mixed methods approach to support the application of the influence of a normative landscape, this study examines two research questions: (1) How do regionally normative landscapes influence site-based farming practices? And (2) To what extent do aspects (i.e., crop areas, buffer areas, and living areas) of individual farms contribute to the development of those regionally normative landscape meanings? When examining the first research question, an analysis of 21 interviews with farmers in Wisconsin and Illinois’ Driftless Region revealed two recurrent themes: “road farming” was a common way in which farmers communicated with each other about farm practices, and land-based learning events were opportunities to foster dialogue about farming activities that shape normative ideals. The results from the thematic analysis connect site-based farming practices within a broader regional context. A quantitative analysis of a survey of 82 farmers in the same region indicates that social agreement to evaluate the farming practices of others is strongest for crop areas. Our findings suggest that farmers and professionals wanting to improve conservation outcomes should use local events that reflect sustainable practices to disrupt and re-envision regional norms to spread conservation farming practices.

Applying High-Resolution Satellite and UAS Imagery for Detecting Coldwater Inputs in Temperate Streams of the Iowa Driftless Region

Coldwater streams are crucial habitats for many biota including Salmonidae and Cottidae species that are unable to tolerate warmer water temperatures. Accurate classification of coldwater streams is essential for their conservation, restoration, and management, especially in light of increasing human disturbance and climate change. Coldwater streams receive cooler groundwater inputs and, as a result, typically remain ice-free during the winter. Based on this empirical thermal evidence, we examined the potential of very high-resolution (VHR) satellite and uncrewed aerial system (UAS) imagery to (i) detect coldwater streams using semi-automatic classification versus visual interpretation approaches, (ii) examine the physical factors that contribute to inaccuracies in detecting coldwater habitats, and (iii) use the results to identify inaccuracies in existing thermal stream classification datasets and recommend coverage updates. Due to complex site conditions, semi-automated classification was time consuming and produced low mapping accuracy, while visual interpretation produced better results. VHR imagery detected only the highest quality coldwater streams while lower quality streams that still met the thermal and biological criteria to be classified as coldwater remained undetected. Complex stream and site variables (narrow stream width, canopy cover, terrain shadow, stream covered by ice and drifting snow), image quality (spatial resolution, solar elevation angle), and environmental conditions (ambient temperature prior to image acquisition) make coldwater detection challenging; however, UAS imagery is uniquely suited for mapping very narrow streams and can bridge the gap between field data and satellite imagery. Field-collected water temperatures and stream habitat and fish community inventories may be necessary to overcome these challenges and allow validation of remote sensing results. We detected >30 km of coldwater streams that are currently misclassified as warmwater. Overall, visual interpretation of VHR imagery it is a relatively quick and inexpensive approach to detect the location and extent of coldwater stream resources and could be used to develop field monitoring programs to confirm location and extent of coldwater aquatic resources.

Effects of non-native Salmo trutta and multiscale habitat factors on native fishes in the Driftless Area

We collected fishes and habitat data at 138 streams to evaluate the effects of introduced brown trout ( Salmo trutta) and habitat conditions on occurrence, detection, abundance, and size structure of sculpin ( Cottus spp.), longnose dace ( Rhinichthys cataractae), and southern redbelly dace ( Chrosomus erythrogaster) in the Driftless Area, USA. Sculpin detection decreased with increasing stream velocity, whereas southern redbelly dace detection increased with stream depth. Sculpin occupancy declined with increasing stream temperature and velocity and increased with increasing forested land, boulder substrate, and brown trout length and abundance. Longnose and southern redbelly dace occupancy and abundance declined with increasing brown trout abundance and occupancy increased with stream temperature. Longnose dace occupancy also increased with increasing stream temperature and cobble substrate and declined with increasing elevation. Native fish size structure was unrelated to brown trout presence. Our results suggest that effects of brown trout are not ubiquitous across native fishes and depend on abiotic conditions and species-specific habitat requirements, highlighting the need to consider both biotic and abiotic conditions when balancing native species conservation with introduced sportfish management.

Defrocking the false father of the ‘Driftless Area’, USA

The Driftless Area is a designation popular in American promotional tourist literature for an area in four contiguous American states, Minnesota, Wisconsin, Iowa and Illinois, that were not glaciated during the latest ice advance. Geographer Lawrence Martin published several articles asserting that geologist William H. Keating first discovered this area in 1823, an error that has crept into subsequent accounts. But historical evidence goes to show that three geologists, Roland D. Irving, Newton H. Winchell and Thomas C. Chamberlin, were simultaneous originators of the concept as we understand it today, about the year 1877.

Examining Suitable Habitat and the Potential for Establishment of Introduced Epipactis helleborine in Southeastern Minnesota

Nonnative, invasive plant species have been notoriously problematic for many ecosystems by outcompeting native plant species and disrupting habitat for insects and other animal life. Within the last decade, a nonnative orchid, Epipactis helleborine L. Crantz (Orchidaceae), has become increasingly present in Minnesota and is considered invasive in some eastern states, including Wisconsin. This study provides insights into the presence and habitat preferences of E. helleborine in Winona County, in southeastern Minnesota. A large portion of Winona County lies within the Driftless region, which is characterized by bluff land and unique plant communities that have been greatly impacted by invasive species. This study used MaxEnt software to create a habitat suitability model for E. helleborine using six environmental predictors: elevation, slope, aspect, soil type, land cover, and distance to roads. The results were a model with high habitat suitability predictability with elevation and slope being the most important predictors, whereas other variables contributed little to the final model. The final model showed relatively small areas with high suitability, where management efforts should be concentrated. Based on the model, this species does not seem to be a substantial threat to areas of great conservation concern, such as southwestern facing bluff prairies.

A Q‐method survey of stream restoration practitioners in the Driftless Area, USA

AbstractStream restoration has become increasingly common, both globally and specifically in the United States. Though stream restoration has become a common freshwater management practice, there are debates around what constitutes “success” in restored systems and whether this success should incorporate both scientific and stakeholder‐defined endpoints. In our study context, the Upper Mississippi River Basin's Driftless Area, conflicts over stream restoration practices often center on the management and use of Driftless Area streams, as practitioners navigate competing perspectives about restoration approaches alongside tensions over whose needs and interests should be prioritized in restoration planning and implementation. Based on the importance of stream restoration practitioner perspectives for mediating uncertainty and shaping on‐the‐ground projects, we asked (a) What are the main areas of conflict that emerge around Driftless Area stream restoration? (b) Can stream restoration practitioners be categorized into distinct groups based on their varying perspectives on stream restoration practices in the Driftless Area? (c) If so, what are these groups and how do they map onto the main areas of stream restoration conflict in the Driftless Area? We used Q‐method to identify and describe four perspectives about stream restoration practices and priorities in the Driftless Area. Our results suggest that (a) the differences between groups are related to concerns about best practices for stabilizing streambanks and post‐restoration monitoring. We found that (b) all four Q‐method identified groups agree that floodplain‐stream channel reconnection is an important aspect of restoration projects and that erosion is a big concern in the Driftless Area.

Evaluation of two fish-based indices of biotic integrity for assessing coldwater stream health and habitat condition in Iowa’s driftless area, USA

Evaluation of two fish-based indices of biotic integrity for assessing coldwater stream health and habitat condition in Iowa’s driftless area, USA

Broadscale Population Structure and Hatchery Introgression of Midwestern Brook Trout

AbstractBrook Trout Salvelinus fontinalis have faced significant declines throughout their native range and have been stocked in Midwestern waters since the late 1800s to offset such losses. Several studies have investigated the genetic effects of these stockings, but these efforts have been confined to relatively small spatial scales. In this study, we compiled 8,454 Brook Trout microsatellite genotypes from 188 wild Midwestern populations and 26 hatchery strains to provide novel insights of broadscale population structure, regional patterns of genetic diversity, and estimates of hatchery introgression for inland Wisconsin populations. Our results indicate high levels of differentiation among our study populations, a lack of hydrological population structuring, lower estimates of genetic diversity in the Driftless Area, and that hatchery introgression has been largely confined to regions of inland Wisconsin that have been heavily affected by anthropogenic disturbances (i.e., the Driftless Area). We also provide evidence that populations may be able to purge hatchery‐derived alleles, discuss possible mechanisms behind this phenomenon, and consider their relevance to accurate estimation of hatchery introgression. Collectively, these results summarize the genetic effects of over a century of anthropogenic disturbance on native Brook Trout populations and emphasize the importance of integrating historical data into contemporary genetic research of intensively managed species.

Factors Associated with Detection and Distribution of Native Brook Trout and Introduced Brown Trout in the Driftless Area of Iowa

AbstractFish populations at the fringe of their geographic range often inhabit marginal habitats and are vulnerable to ecological disturbances, such as species invasion, land cover conversion, and climate change. The Driftless Area of northeastern Iowa, USA represents the southwestern edge of the native range of Brook Trout Salvelinus fontinalis, where endemic populations have been greatly reduced due to habitat degradation and introduced Brown Trout Salmo trutta. Therefore, documenting Brook Trout occurrence patterns at the southern tip of their range may prove useful for the conservation of peripheral populations. We fitted single‐species occupancy models at multiple spatial scales to estimate the relative effects of biotic (e.g., Brown Trout density) and habitat (instream, riparian, and watershed) variables on Brook and Brown Trout occupancy to predict their current distribution in the Iowa Driftless Area. Species occurrence and physical habitat data were collected at 138 stream segments of the Upper Iowa, Yellow, and Little Maquoketa River watersheds (8‐digit hydrologic unit codes) during May–September in 2018 and 2019. Brook Trout occupancy was low (19 of 138 sites) and affected by local (instream and riparian) habitat covariates, particularly August–September stream temperatures, but no adverse effects of Brown Trout density were detected. Brown Trout occupied 54% of streams (74 of 138 sites), and occupancy was influenced by a combination of local‐scale (mean stream velocity, percentage of run macrohabitat, and August–September stream temperatures) and catchment‐scale (percent forested land cover and upstream catchment area) habitat variables. Our results provide evidence that instream thermal conditions are a critical determinant of Brook Trout distribution, while Brown Trout exhibit plasticity in habitat suitability and increased colonization in areas where they are introduced. Given the dependence of Brook Trout on cold stream temperatures, the projected loss of thermally suitable habitats due to climate change may facilitate their replacement by naturalized Brown Trout at the southwestern extent of their range.

Using vis-NIR and pXRF data to distinguish soil parent materials – An example using 136 pedons from Wisconsin, USA

Many soils have two or more parent materials. It is not always possible to distinguish these materials in a soil pit or in the field. Here we present a study in the Driftless Area of Wisconsin, where soils were developed in loess covering the weathered impurities of dolostone, termed terra rossa. We evaluated the geochemical signature of 136 pedons with loess (A and Bt) and/or terra rossa (2Bt) horizons and developed decision tree models to distinguish the Bt and 2Bt horizons from different geochemical indicators. In total 409 samples were collected from A, Bt, and 2Bt horizons and the samples were scanned using vis-NIR and pXRF spectrometers to obtain the color information, elemental data, and to calculate weathering indices. The Munsell color, texture, total carbon (TC), total nitrogen (TN), and pH were measured in the laboratory. Twenty one types of input data were compared in decision tree models. It was found that the 2Bt horizons had higher clay, pH, Mg, Al, Fe, Ca, Mn, Zn, Rb, CTR, and Ti/Zr than the loess A and Bt horizons. The Ruxten index (R), clay, horizon thickness (HT), CaO/TiO2 (CTR), and Ti/Zr were robust variables to distinguish loess Bt and terra rossa 2Bt using a decision tree model. However, similarities in the values of some elements and weathering indices compromised the characterizations of Bt and 2Bt horizons, which is the result of mixing of parent materials through bioturbation over time. It can be concluded that pXRF and vis-NIR spectra can be used to distinguish parent materials in soil profiles, and pXRF spectra had slightly better overall accuracy than vis-NIR spectra.

The Flora of a Mesic Forest Remnant in Iowa's Paleozoic Plateau: Malanaphy Springs State Preserve (Winneshiek County, Iowa)

We present the results of a floristic inventory and qualitative descriptions of the forest communities occurring in Malanaphy Springs State Preserve (MSSP), located in the Paleozoic Plateau of northeastern Iowa. Most of the 25.9-ha preserve is a mature mesic to dry-mesic deciduous forest community occurring on a steep slope adjacent to the Upper Iowa River. The preserve also contains a small floodplain forest as well as a small highly disturbed forest on the upland. We documented 422 plant taxa in our surveys, including 52 non-vascular taxa, 14 seedless vascular taxa, 3 gymnosperms, and 353 angiosperms. Eighty-seven percent of the vascular plant taxa are native, and 21% of the species have an Iowa coefficient of conservatism score of 7 or higher. Five species are listed by the Iowa Department of Natural Resources as endangered, threatened, or of special concern in the state. This survey provides critical baseline data needed to document future changes in the plant communities of MSSP. We conclude that this preserve is an important example of high-quality mesic deciduous forest communities in Iowa. We further conclude that the species diversity of the preserve is threatened by the cumulative impacts of habitat loss, high levels of deer herbivory, invasive species, nitrogen deposition, and climate change and that active management and strategic policy decisions will be needed to preserve native plant species diversity.

Rapid changes in agricultural land use and hydrology in the Driftless Region

AbstractAnnual cropping systems are common in the Driftless Region of the U.S. Midwest, but soil degradation is prone to happen in such systems due to the rugged topography of the region. Recent rapid increases in row crop area have been noted in this region, with annual precipitation and hydrologic extremes on the rise in recent decades. The aim of this research to use geospatial datasets and tools in order to assess the regional trends in land use, precipitation, and hydrologic change and quantify the relationship between these environmental trends. Between 2006 and 2017, substantial row crop expansion of 10,000 ha or more was common across HUC 8 (Hydrologic Unit Code 8) watersheds in our study area. Expansion occurred mainly on steeper slopes, converting existing grasslands or alfalfa (Medicago sativa L.) to row crops. Classifying land as planted (in row crops), plantable (in row crops or could be converted), and unplantable (unable to be converted) revealed that Driftless Region watersheds have ∼30–50% of plantable land available for future expansion. Annual precipitation was highly variable during this time period but had a general increasing trend. On average, precipitation showed higher correlation to streamflow compared to row crop expansion across 27 USGS river gage drainage basins in our study area. However, when the increase in row crop area was significant and was accompanied by increasing precipitation, stronger correlation between row crop area and annual streamflow was exhibited. This finding suggests that row crop expansion acts to enhance the effects of increasing precipitation on local hydrology.