Darren Ficklin

• PhD
• Professor (Assistant) at Indiana University Bloomington

Future flood risk assessment has primarily focused on heavy rainfall as the main driver, with the assumption that projected increases in extreme rain events will lead to subsequent flooding. However, the presence of and changes in vegetation have long been known to influence the relationship between rainfall and runoff. Here, we extract historical...

Most readily available land use/land cover (LULC) data are developed using growing season remote sensing images often at annual time steps, but seasonal changes in remote sensing data can lead to inconsistencies in LULC classification, which could impact geospatial models based on LULC. We used the Dynamic World near-real-time global LULC dataset t...

Vapour pressure deficit (VPD) is a critical measure of the atmospheric demand for water and can be used to assess short‐term and seasonal drought. To provide for probabilistic comparisons of VPD across space and time, we develop a Standardized Vapor Pressure Deficit Index (SVPDI). Similar to the way that other standardised drought indices are used,...

Citizen science yields increased scientific capacity in exchange for science literacy and promises of a more responsive science to society’s needs. Yet, citizen science projects are criticized for producing few scientific outputs and having exploitative relationships with the citizens who participate. In the eagerness to capture new data, scientist...

Forests around the world are experiencing changes due to climate variability and human land use. How these changes interact and influence the vulnerability of forests are not well understood. In the eastern United States, well‐documented anthropogenic disturbances and land‐use decisions, such as logging and fire suppression, have influenced forest...

Citizen science is personal. Participation is contingent on the citizens’ connection to a topic or to interpersonal relationships meaningful to them. But from the peer-reviewed literature, scientists appear to have an acquisitive data-centered relationship with citizens. This has spurred ethical and pragmatic criticisms of extractive relationships...

An exponential rise in the atmospheric vapour pressure deficit (VPD) is among the most consequential impacts of climate change in terrestrial ecosystems. Rising VPD has negative and cascading effects on nearly all aspects of plant function including photosynthesis, water status, growth and survival. These responses are exacerbated by land–atmospher...

The emergence of billions of periodical cicadas affects plant and animal communities profoundly, yet little is known about cicada impacts on soil carbon fluxes. We investigated the effects of Brood X cicadas (Magicicada septendecim, M. cassinii and M. septendeculain) on soil CO2 fluxes (RS) in three Indiana forests. We hypothesized RS would be sens...

The Midwest of the USA is a highly productive agricultural region, in part due to the installation of perforated subsurface pipes, known as tile drains that remove excess water from wet soils. Tile drains rapidly move water to nearby streams, influencing how quickly streamflow rises and falls (i.e., streamflow “flashiness”). Currently, there are no...

Most readily available landuse/landcover (LULC) data are developed using growing season remote sensing images often at annual time steps. We used the Dynamic World near real-time global LULC dataset to compare how geospatial environmental models of water quality and hydrology respond to growing vs. non-growing season LULC for temperate watersheds o...

Rain-on-snow (ROS) melt events reduce the amount of water stored in the snowpack while also exacerbating flooding. The hydrologic implications of changing ROS events in a warming climate, however, are still uncertain. This research used a calibrated and validated Soil and Water Assessment Tool (SWAT) hydrologic model, modified with energy budget eq...

Meteorological drought indices like the Standardized Precipitation Evaporation Index (SPEI) are frequently used to diagnose “ecological drought,” despite the fact that they were not explicitly designed for this purpose. More recently developed indices like the Evaporative Stress Index (ESI), which is based on the degree of coupling between actual t...

Climate change and other human activities are modifying river water temperature globally. A more holistic understanding of river temperature dynamics in an integrated climate–land–hydrology–human framework is urgently needed for sustainable river management and adaptation strategies.

The 2021 emergence of the 17‐year Brood X cicadas (Magicicada septendecim, M. cassinii, and M. septendecula) saw billions of cicadas emerge from the soil throughout the midwestern and eastern United States. The emergence left connected burrows visible at the surface, which are hypothesized to affect near surface hydrologic processes. To investigate...

Study region Watersheds of the Atlantic Coast of the United States (ACUS) spanning a latitudinal range of 30.8°N – 46.5°N Study focus This study assessed climate-induced changes (CMIP5-RCP 8.5) in projected streamflow and water temperature estimates from individual SWAT watershed models across the ACUS territory by mid and end of the century. Seas...

Plain Language Summary Tree rings are often used to estimate past levels of streamflow to better place modern extremes into a historical context. Streamflow has two components, baseflow (flow from groundwater) and stormflow (flow contributed from storms). Here, we use tree rings to estimate past streamflow of the Santee River, South Carolina, USA....

Most readily available landuse/landcover (LULC) data are developed using growing season remote sensing images and/or annual time steps. We used new Dynamic World near real-time global LULC to compare how geospatial environmental models of water quality and hydrology respond to growing vs. non-growing season LULC data. Non-growing season LULC had mo...

Most readily available landuse/landcover (LULC) data are developed using growing season remote sensing images often at annual time steps. We used the Dynamic World near real-time global LULC dataset to compare how geospatial environmental models of water quality and hydrology respond to growing vs. non-growing season LULC for temperate watersheds o...

Most readily available landuse/landcover (LULC) data are developed using growing season remote sensing images often at annual time steps. We used the Dynamic World near real-time global LULC dataset to compare how geospatial environmental models of water quality and hydrology respond to growing vs. non-growing season LULC for temperate watersheds o...

Rain-on-snow (ROS) melt events reduce the amount of water stored in the snowpack while also exacerbating flooding. The hydrologic implications of changing ROS events in a warming climate, however, are still uncertain. This research used a calibrated and validated Soil and Water Assessment Tool (SWAT) hydrologic model, modified with energy budget eq...

Global warming intensifies the hydrological cycle by altering the rate of water fluxes to and from the terrestrial surface, resulting in an increase in extreme precipitation events and longer dry spells. Prior hydrological intensification work has largely focused on precipitation without joint consideration of evaporative demand changes and how pla...

Water potential directly controls the function of leaves, roots and microbes, and gradients in water potential drive water flows throughout the soil–plant–atmosphere continuum. Notwithstanding its clear relevance for many ecosystem processes, soil water potential is rarely measured in situ, and plant water potential observations are generally discr...

In many cold climates, rain-on-snow (ROS) events are associated with severe snowmelt and flooding. ROS events also rapidly deplete snowpacks, reducing the potential for subsurface water storage later in the year. We incorporated a simple, easily transferable energy-balance ROS model into the Soil and Water Assessment Tool (SWAT) to assess how ROS m...

Water temperature is an important indicator of the health of terrestrial and aquatic ecosystems and influences numerous biological and chemical processes that affect water quality, the health and productivity of biota, and other ecosystem services. In this study, we improved the Soil and Water Assessment Tool (SWAT) model to explicitly consider the...

Transformative research in freshwater ecosystems requires successfully engaging an array of stakeholders. Local community members are experts of the social and ecological systems in which they are embedded and can improve scientific research in many ways. We outline several steps for researchers to engage local experts specifically by focusing on m...

Changes to water resources are critical to all sectors of the economy. Climate change will affect the timing and quantity of water available in the environment as well as have an adverse effect on the quality of that water. Floods, droughts, and changing patterns of water scarcity—when water is not available in sufficient enough quantities or of a...

The selection of calibration and validation time periods in hydrologic modeling is often done arbitrarily. Nonstationarity can lead to an optimal parameter set for one period which may not accurately simulate another. However, there is still much to be learned about the responses of hydrologic models to nonstationary conditions. We investigated how...

Small streams often lack reliable hydrological data. Environmental agencies play a key role in providing such data; however, these agencies are often challenged by the growing monitoring needs and lack of funding. Given the spatial mismatch between observed data and small watersheds/headwaters, local volunteers can act as potentially valuable resea...

Plain Language Summary To study past climates, scientists use indicators such as tree‐ring widths that are related to temperature, precipitation, or streamflow. While these indicators usually are very reliable, they sometimes do not perform as well with extreme events such as intense droughts and wet periods. Here, we adopt a method that can correc...

Plain Language Summary Increasing air temperatures have resulted in an intensification, or acceleration, of the terrestrial hydrologic cycle, which is defined as an increase of the water fluxes (precipitation and evapotranspiration) between the surface and the atmosphere. Efforts to quantify hydrologic intensification have traditionally only consid...

Elevated vapor pressure deficit (VPD) due to drought and warming is well-known to limit canopy stomatal and surface conductance, but the impacts of elevated VPD on ecosystem gross primary productivity (GPP) are less clear. The intrinsic water use efficiency (iWUE), defined as the ratio of carbon (C) assimilation to stomatal conductance, links veget...

Aim Streamflow and water temperature are primary variables influencing the distribution of freshwater taxa. Climate‐induced changes in these variables are already causing shifts in species distributions, with continued changes projected in the coming decades. The Mobile River Basin (MRB), located in the southeastern United States, contains some of...

Ongoing changes in climate are expected to alter current species’ habitat and potentially result in shifts in species distributions. While climatic conditions are important to a species’ ability to persist in an area, for many taxa, other environmental factors, such as geology, land cover, and topography, are also important for providing suitable h...

Tree-ring reconstructions of streamflow can provide long-term perspectives of flow variability that may be useful in management strategies for water resources. Relative to other portions of the United States, there is a dearth of tree-ring based streamflow reconstructions in the Midwest. The Wabash River is an important water resource in Indiana an...

Hydrologic regimes and water temperatures are primary predictors of freshwater species occurrence. Although these variables have been demonstrated to be important in regulating species diversity at particular locations, whether species occurrences across lotic habitats within a single, relatively small watershed can predict the full geographic exte...

Climate induced changes in streamflow and stream temperature are likely to have significant effects on the physical and biological aspects of freshwater systems. Quantifying these changes in hydrologic conditions is therefore paramount for proper management of water resources and aquatic ecosystems. This study assesses the impacts of climate change...

The Gulf Coast watersheds in the United States contain some of the highest levels of biodiversity of all freshwater systems in North America. Developing environmental management policies to protect and preserve these ecosystems makes the study of the impacts of projected climate change on the future hydrologic cycle crucial. We used the Soil and Wa...

Severe droughts can impart long‐lasting legacies on forest ecosystems through lagged effects that hinder tree recovery and suppress whole‐forest carbon uptake. However, the local climatic and edaphic factors that interact to affect drought legacies in temperate forests remain unknown. Here, we pair a dataset of 143 tree ring chronologies across the...

Tropical rainforests play a central role in the Earth system by regulating climate, maintaining biodiversity, and sequestering carbon. They are under threat by direct anthropogenic impacts like deforestation and the indirect anthropogenic impacts of climate change. A synthesis of the factors that determine the net ecosystem exchange of carbon dioxi...

Stream temperature is one of the most important factors for regulating fish behavior and habitat. Therefore, models that seek to characterize stream temperatures, and predict their changes due to landscape and climatic changes, are extremely important. In this study, we extend a mechanistic stream temperature model within the Soil and Water Assessm...

Significance Climate change is expected to alter streamflow volume and variability in watersheds throughout the world, which will have impacts on agricultural, aquatic, and urban environments. Human modifications such as the building of reservoirs and the extraction of water for agricultural and urban uses, however, are thought to mask climate-indu...

Decision-support tools (DSTs) are often produced from collaborations between technical experts and stakeholders to address environmental problems and inform decision making. Studies in the past two decades have provided key insights on the use of DSTs and the importance of bidirectional information flows among technical experts and stakeholders – a...

Changes in streamflow volume and stream temperature coupled with projected changes in climate are likely to have significant effects on aquatic species. Quantifying these changes in hydrologic conditions is paramount for proper management of water resources and aquatic ecosystems. Here, we used the Soil and Water Assessment Tool (SWAT) with a hydro...

Stream temperature is an important indicator for biodiversity and sustainability in aquatic ecosystems. The stream temperature model currently in the Soil and Water Assessment Tool (SWAT) only considers the impact of air temperature on stream temperature, while the hydroclimatological stream temperature model developed within the SWAT model conside...

Climate change is likely to have significant effects on the water cycle of the Gulf Coast watersheds in the United States, which contain some of the highest levels of biodiversity of all freshwater systems in North America. Understanding potential hydrologic responses to continued climate change in these watersheds is important for management of wa...

The synoptic processes that end droughts are poorly understood, yet have significant climatological implications. Here we examined the spatio-temporal patterns of rapid drought cessation (RDC) in the southeastern United States during the1979–2013 warm season (April–November) for three storm types: Frontal, Tropical and Airmass. We defined RDC as a...

Ongoing increases in air temperature and changing precipitation patterns are altering water temperatures and flow regimes in lotic freshwater systems, and these changes are expected to continue in the coming century. Freshwater taxa are responding to these changes at all levels of biological organization. The generation of appropriate hydrologic an...

Many globally important groundwater aquifers are under considerable stress as withdrawals, predominantly for irrigation, outpace recharge. Meanwhile, groundwater policy to address the common-pool resource losses remains in its nascent stage. This study analyzes a recent and unique bottom-up effort to self-impose a groundwater pumping fee in San Lui...

Changes in long-term, montane actual evapotranspiration (ET) in response to climate change could impact future water supplies and forest species composition. For scenarios of atmospheric warming, predicted changes in long-term ET tend to differ between studies using space-for-time substitution (STS) models and integrated watershed models, and the i...

The geographic variability in the partitioning of precipitation into surface runoff (Q) and evapotranspiration (ET) is fundamental to understanding regional water availability. The Budyko equation suggests this partitioning is strictly a function of aridity, yet observed deviations from this relationship for individual watersheds impede using the f...

Study region: The Haw River basin in the North Carolina Piedmont. Study focus: Simulation of hydrologic change by projected CO2 and climate using the Soil and Water Assessment Tool (SWAT) hydrologic model. Biases of climate output from the North American Regional Climate Change Assessment Program (NARCCAP) were corrected using the LOCal Intensity (...

Stream temperature is an important indicator for biodiversity and sustainability in aquatic ecosystems. The stream temperature model currently in the Soil and Water Assessment Tool (SWAT) only considers the impact of air temperature on stream temperature, while the hydroclimatological stream temperature model developed within SWAT model considers h...

Climate change has and will continue to impact the magnitude and timing of streamflow throughout the world. While streamflow timing of western United States watersheds has shifted earlier in mountainous snow-dominated watersheds due to earlier snowmelt, timing for rain-dominated coastal watersheds has shifted to later in the year. Despite these dis...

Land use and land cover (LULC) change from forest to urban impervious cover can affect watershed hydrology by altering the rates of evapotranspiration, infiltration, surface runoff, and groundwater recharge. This research evaluated the impact of LULC change on watershed scale hydrologic behavior under different development scenarios within a hydrol...

Land use and land cover (LULC) change from forest to urban impervious cover can affect watershed hydrology by altering the rates of evapotranspiration, infiltration, surface runoff, and groundwater recharge. This research evaluated the impact of LULC change on watershed scale hydrologic behavior under different development scenarios within a hydrol...

Via air temperature increases and relative humidity changes, climate change will modify vapor pressure deficit (VPD), which is an important determinant of water vapor and CO2 exchange between the land surface and atmosphere. VPD is the difference between the water vapor the air can hold at saturation (es) and the actual amount of water vapor (ea)....

Characterization of the uncertainty and sensitivity of model parameters is an essential facet of hydrologic modeling. This article introduces the multi-objective evolutionary sensitivity handling algorithm (MOESHA) that combines input parameter uncertainty and sensitivity analyses with a genetic algorithm calibration routine to dynamically sample t...

Soil moisture supply and atmospheric demand for water independently limit - and profoundly affect - vegetation productivity and water use during periods of hydrologic stress. Disentangling the impact of these two drivers on ecosystem carbon and water cycling is difficult because they are often correlated, and experimental tools for manipulating atm...

This work presents updated hydrologic projections for the Upper Colorado River Basin (UCRB) using downscaled (approximately 12 km) General Circulation Model (GCM) output from Coupled Model Intercomparison Project – Phase 5 (CMIP5) with a comparison to CMIP3 GCMs. We use the Soil and Water Assessment Tool model to simulate the impacts of end-of-cent...

Characterizing the impacts of climatic change on hydrologic processes is critical for managing freshwater systems. Specifically, there is a need to evaluate how the two major components of streamflow, baseflow and stormflow, have responded to recent trends in climate. We derive baseflow and stormflow for 674 sites throughout the United States from...

Background and AimWe examined the feasibility of projecting future winegrape productivity by using Vitis vinifera L. growth rings as a proxy to winegrape yields.Methods and ResultsWe compared the climate response of V. vinifera radial growth rings and winegrape yields using DENDROCLIM2002. We used the soil moisture model HYDRUS to determine if V. v...

Global climate models (GCMs) have biases when simulating historical climate conditions, which in turn have implications for estimating the hydrological impacts of climate change. This study examines the differences in projected changes of aridity [defined as the ratio of precipitation (P) over potential evapotranspiration (PET), or P/PET] and the P...

Calculating the Palmer Drought Severity Index (PDSI) using the Thornthwaite potential evapo-transpiration (PET) method has come under recent scrutiny for overestimating drought conditions when air temperatures exceed the historical baseline. With increasing air temperatures around the world, calculating the PDSI using the Thornthwaite PET method ma...

The increasingly warmer temperatures and changes in precipitation patterns expected from climatic changes in the Sierra Nevada are projected to drive declines in snowpack, earlier streamflow timing, shifts in evapo-transpiration and soil moisture, and substantial increases in summer stream temperatures with associated declines in water quality. Her...

Statistical downscaling is a commonly used technique for translating large-scale climate model output to a scale appropriate for assessing impacts. To ensure downscaled meteorology can be used in climate impact studies, downscaling must correct biases in the large-scale signal. A simple and generally effective method for accommodating systematic bi...

Data from six monitoring stations were combined with a soil-water dynamics model (HYDRUS 1D) to achieve physically-based estimates of shallow water-table recharge in representative hydropedological settings of the glaciated midwestern U.S.A. Calibration involved inverse modeling that yielded optimized hydraulic parameters. Root mean square errors f...

Most recent climate change impact studies are using Coupled Model Intercomparison Project Phase 5 (CMIP5) projections to replace older generation CMIP3 projections. Here we evaluate whether differences between projections based on comparable high emission pathways of a seven-member general circulation model CMIP3 versus CMIP5 ensemble change our un...

We present high spatial-resolution trends of the Palmer drought severity index (PDSI), potential evapotranspiration (PET), and selected climate variables from 1979–2013 for the contiguous United States in order to gain an understanding of recent drought trends and their climatic forcings. Based on a spatial grouping analysis, four regions of increa...

Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in air temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitats in freshwater systems is critical for predicting aquatic species' responses to changes in...

The effects of climate change on water resources have been studied extensively throughout the world through the use of hydrologic models coupled with General Circulation Model (GCM) output or climate sensitivity scenarios. This paper examines the effects of hydrologic model parameterization uncertainty or equifinality, where multiple unique hydrolo...

We tested a methodology for aggregating soil properties across multiple soil survey areas according to soil taxonomic information available within the Soil Survey Geographic (SSURGO) dataset. Most hydrologic modeling studies using SSURGO assume that soil property data are adequately grouped into a “soil type” that is represented by a map unit k...

The impact of climate change and uncertainty of climate projections from General Circulation Models (GCMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) on streamflow in the Johor River Basin, Malaysia was assessed. Eighteen GCMs were evaluated, and the six that adequately simulated historical climate were selected for an ensemb...

Water temperature is a primary physical factor regulating the persistence and distribution of aquatic taxa. Considering projected increases in temperature and changes in precipitation in the coming century, accurate assessment of suitable thermal habitat in freshwater systems is critical for predicting aquatic species responses to changes in climat...

Stream temperature is one of the most influential parameters impacting the survival, growth rates, distribution, and migration patterns of many aquatic organisms. Distributed stream temperature models are crucial for providing insights into variations of stream temperature for regions and time periods for which observed data do not exist. This stud...

Bracketing the uncertainty of streamflow and agricultural runoff under climate change is critical for proper future water resource management in agricultural watersheds. This study used the Soil and Water Assessment Tool (SWAT) in conjunction with a Latin hypercube climate change sampling algorithm to construct a 95% confidence interval (95CI) arou...

In the Upper Colorado River Basin (UCRB), the principal source of water in the southwestern U.S., demand exceeds supply in most years, and will likely continue to rise. While General Circulation Models (GCMs) project surface temperature warming by 3.5 to 5.6°C for the area, precipitation projections are variable, with no wetter or drier consensus....

Key Points Stream temperature is expected to increase by 1 to 5.5 oC Dissolved oxygen concentrations are expected to decrease Sediment concentrations are projected to decrease by about 50%

The assessment of hydrologic responses to climate change is required in watershed management and planning to protect water resources and environmental quality. This study is designed to evaluate and enhance watershed modeling approach in characterizing climate change impacts on water supply and ecosystem stressors. Soil and Water Assessment Tool (S...

Agricultural pollutant runoff is a major source of water contamination in California's Sacramento River watershed where 8500 km2 of agricultural land influences water quality. The Soil and Water Assessment Tool (SWAT) hydrology, sediment, nitrate and pesticide transport components were assessed for the Sacramento River watershed. To represent flood...

The curve number and Green-Ampt rainfall-runoff models were compared in the highly agricultural San Joaquin River watershed in California using the Soil and Water Assessment Tool (SWAT). The rainfall-runoff models were left uncalibrated to objectively assess model performances; however, streamflow simulations showed high accuracy compared to observ...

The Californian Mono Lake Basin (MLB) is a fragile ecosystem, for which a 1983 ruling carefully balanced water diversions with ecological needs without the consideration of global climate change. The hydroclimatologic response to the impact of projected climatic changes in the MLB has not been comprehensively assessed and is the focus of this study...

Sierra Nevada snowmelt and runoff is a key source of water for many of California’s 38 million residents and nearly the entire population of western Nevada. The purpose of this study was to assess the impacts of expected 21st Century climatic changes in the Sierra Nevada at the subwatershed scale, for all hydrologic flow components, and for a suite...

This study presents a comprehensive investigation of the State Soil Geographic Database (STATSGO) and the Soil Survey Geographic Database (SSURGO) soil databases for their applications in hydrologic modeling practices, and provides detailed instructions on soil data aggregation. Two types of soil data aggregations are developed and improved for the...

Climate change may significantly affect the hydrological cycle and water resource management, especially in arid and semi-arid regions. In this paper, output from the Providing Regional Climates for Impacts Studies (PRECIS) regional climate model were used in conjunction with the Soil and Water Assessment Tool (SWAT) to analyse the effects of clima...

We develop a stream temperature model within the Soil and Water Assessment Tool (SWAT) that reflects the combined influence of meteorological (air temperature) and hydrological conditions (streamflow, snowmelt, groundwater, surface runoff, and lateral soil flow) on water temperature within a watershed. SWAT currently uses a linear air-stream temper...