Earth Sciences Commons^™

Hydroclimatic Whiplash Across The Contiguous United States: Characterizing Wet–Dry Transitions In Pdsi And Phdi, James Lam, Thomas Christopher Piechota

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Hydroclimatic whiplash, characterized by rapid transitions between wet and dry conditions, poses a growing challenge for water resource management and ecosystem stability. However, the spatial and statistical characteristics of wet–dry transitions across the contiguous United States are not fully understood. This study analyzed Palmer Drought Severity Index (PDSI) and Palmer Hydrological Drought Index (PHDI) records from 344 NOAA climate divisions spanning 1895–2024. Whiplash was defined as a transition between severe drought and severe wetness within 12-month rolling windows. Statistical descriptors including lag-1 autocorrelation, variance, and skewness were evaluated for whiplash and non-whiplash windows to assess differences between them. Whiplash hotspots …

Plant-Water Relationships Of Crested, Pubescent, Slender, And Western Wheatgrass, A B. Frank

IGC Proceedings (1977-2023)

Objectives were to characterize development of water stress in the field and in controlled environments; to determine stress ef­fects on transpit"ation (E), stomata} conductance (C), leaf water potential (LWP), leaf osmotic potential (LOP), and photosyn­thesis (P); and to relate measured changes to drought tolerance in crested wheatgrass (Agropyron desertorom [Fisch.] Schult.), slender wheatgrass (A. trachycaulum [Link] Malte.), pubescent wheatgrass (A. intermedium var. trichophorum [Link] Haloc), and western wheatg:rass (A. smithii Rydb. ). Both L WP and LOP decreased for all species as soil water potential decreased, but not in a 1: 1 ratio indicative of maximum osmotic adjustment. The LWP …

Hail As An Ecological Factor In The Increase Of Pricklypear Cactus, W A. Laycock

IGC Proceedings (1977-2023)

Detached joints or pads of plains pricklypear cactus (Opuntia pov,acantha) can root and form new plants. However, few data exist to quantify this phenomenon or to describe conditions under which rooting takes place. A severe hailstorm at the Central Plains Experimental Range in northeastern Colorado on 31 July 1978 broke segments from plants of plains pricklypear. This oc­currence provided an opportunity to determine the amount of joint dispersal and rooting from a natural destructive event. Cactus joints detached and scattered by the force of the hail were counted on permanent belt transects established in two pastures having different pricklypear populations. …

Harnessing Backcasting To Identify Drivers Of Critical Warming At Hoover Dam Using Hydrodynamic And Machine Learning Models, Eunice Ledres

UNLV Theses, Dissertations, Professional Papers, and Capstones

Elevated water temperatures can pose a significant threat to dam infrastructure, potentially damaging turbines, overheating internal components, and forcing generator shutdowns. This study uses a backcasting framework to evaluate how future scenarios may result in elevated water temperatures. Backcasting defines undesirable outcomes and works backward to identify the conditions that lead to them. The developed backcasting framework integrates 3D physics-based simulations with a Long-Short Term Memory (LSTM)surrogate model and SHapely Additive exPlanations (SHAP) interpretation. The combination captures temporal water temperature dynamics and quantifies the contributions of different drivers to elevated water temperature releases. As proof of concept, these methods are …

Examining Extremes: A Comparison Between Machine Learning Based Southwestern Conus Seasonal Drought And High Fire Risk Event Synoptic Climatologies, Ethan M. Greenberg

School of Natural Resources: Dissertations, Theses, and Student Research

The Southwestern United States (SW CONUS), comprised of California, Arizona, Nevada, and Utah, is a vast region that tens of millions of people call home. Hosting ecosystems ranging from grasslands and shrublands to temperate forests and climate zones ranging from Mediterranean climates to arid deserts, the region is nearly unanimously prone to intense droughts and devastating wildfires. While fire weather conditions and drought are often studied separately or mentioned as background conditions for the other, there are relatively few studies that compare the typical meteorological conditions between the two. This study aims to more closely understand the meteorological relationship between …

Passive Microwave Remote Sensing Of Flash Drought Impacts On Vegetation, Quinton R. Deppert

School of Natural Resources: Dissertations, Theses, and Student Research

In 2002, Dr. Mark Svoboda characterized a new form of drought known as flash drought. Flash drought was defined as a rapid decline in vegetation health caused by severe heat and drought. In recent years, attempts to quantify the impacts of flash drought via precipitation, soil moisture, evapotranspiration, and temperature indicators have proliferated. What has rarely been quantified is what the rapid decline in vegetation health amid flash drought looks like through remote sensing. This is because vegetation health indices like the Normalized Difference Vegetation Index (NDVI) are derived from the visible and infrared regions of the electromagnetic spectrum and …

Geol 12 Natural Disasters Syllabus, Anestoria Shalkowski

Open Educational Resources

Hazards are events which have the capabilities to damage property and or life. Understanding natural hazards and how these can become disasters are important in reducing the impacts of such events. This syllabus provides a description of the material to be examined and the expected student outcomes upon completion of the course.

Co2 Exchange Of The Abovegrass And Belowground Components Of Kleingrass (Panicum Coloratum L.) During Drought In The Northern Chihuahuan Desert, William B. Sisson

IGC Proceedings (1977-2023)

The effect a 52 day drought had on the die! whole-plant carbon balance of kleingrass (Panicum coloratum L.) growing in the northern Chihuahuan desert was determined. Whole-plant CO2 inputs (photosynthesis) and outputs (belowground and aboveground respiration) were measured on day 52 of the drought (June 23, 1981) and 2 days following 1.12 cm of precipitation that occurred on June 24, 1981. Although net photosynthesis rates were severely depressed on June 23, a positive whole-plant carbon balance was determined prior to and following the rain. On a whole-plant basis,.002 g C/g DW/day was gained on June 23 and .015 g …

Remote Sensing-Based Assessment Of Evapotranspiration Patterns In A Unesco World Heritage Site Under Increasing Water Competition, Maria C. Moyano, Monica Garcia, Luis Juana, Laura Recuero, Lucia Tornos, Joshua B. Fisher, Néstor Fernández, Alicia Palacias-Orueta

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

In water-scarce regions, natural ecosystems and agriculture increasingly compete for limited water resources, intensifying stress during periods of drought. To assess these competing demands, we applied a modified PT-JPL model that incorporates the thermal inertial approach as a substitute for relative humidity (RH) in estimating soil evaporation—a method that significantly outperforms the original PT-JPL formulation in Mediterranean semi-arid irrigated areas. This remote sensing framework enabled us to quantify spatial and temporal variations in water use across both natural and agricultural systems within the UNESCO World Heritage site of Doñana. Our analysis revealed an increasing evapotranspiration (ET) trend in intensified agricultural …

Atmospheric Teleconnection Patterns And Hydrological Whiplashes In The Western U.S., Wenzhao Li, Surendra Maharjan, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

The Western U.S. is undergoing notable transformations in its hydrological patterns, distinguished by rising variability and recurrent “whiplash” shifts between extreme wet and dry phases. Our comprehensive analysis of 469 streamflow stations from 1981 to 2023 reveals a substantial increase in hydrological whiplash events, with a peak of 206 stations experiencing dry-to-wet whiplash in the early 1990s. We establish strong links between these streamflow extremes and sub-seasonal to seasonal teleconnection factors, particularly the Western Pacific Oscillation (WP) and Eastern Pacific/North Pacific Oscillation (EPO). Additionally, we demonstrate the combined impacts of the El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO), …

Special Enhancements Using Noaa Satellite Data To Evaluate Grasslands Of Western Canada, H Mccartney, J Whiting, J Polson

IGC Proceedings (1977-2023)

The grazing and hay lands of Saskatchewan, a Province in western Canada, extend from the wide open short grass prairie of the south to the northern roughland bush pastures of the Aspen Parkland (Populus tremuloides). These areas total 7,853,000 ha. This study is part of a continuing effort directed towards the development of operational remote sensing analysis techniques for the estimation of grazing conditions in both native and seeded pastures in Saskatchewan. Multi-spectral remotely sensed data from satellites has proven useful in assessing crop vigour. In most cases, where drought assessment or monitoring was required, large land areas were involved …

Summerpack*, A Computer Package For Sheep And Pasture Management Over The Summer/Autumn Period In A Mediterranean Environment, J.P G. Orsini

IGC Proceedings (1977-2023)

The south-western part of Western Australia has a Mediterranean type climate characterized by a dry summer/autumn period that can extend over more than six months. The quantity and the quality of the dry pastures progressivily deteriorate from senescence until the break of season when germination occurs. Although dry adult sheep usually maintain weight in the first two months, weight losses can be high in autumn unless supplements are fed. It is important for farmers at the beginning of summer to obtain an estimate of the amount of supplements they need to purchase or keep in storage and what would be …

The 1991 California 'Miracle March': Precipitation Myth Or Miracle?, Cody D. Poulsen, Rachel E.S. Clemesha, Ian M. Howard, Alexander Gershunov, Michael D. Dettinger, Zhenhai Zhang, Rosa Luna-Nino, David W. Stahle, Ralph F. Martin

Geosciences Faculty Publications and Presentations

The term 'Miracle March' is colloquially used in California to describe an anomalously wet spring that alleviates drought conditions caused by a winter precipitation deficit. This study centers on the influential water year 1991, which is the standard reference point for this phenomenon. The spring precipitation impact on water year totals and the geographic extent of the spring precipitation anomaly during the 1991 'Miracle March' (MM91) is without equal in the observational record. This exceptional precipitation episode was initiated by a week-long sequence of extreme atmospheric rivers that started landfalling on February 27th. To this day, MM91 is routinely referenced …

Unraveling The Causal Influences Of Drought And Crop Production On Groundwater Levels Across The Contiguous United States, Nitin K. Singh, Sheila M. Saia, Ruchi Bhattacharya, Hoori Ajami, David M. Borrok

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Groundwater depletion in agricultural-dominated regions is attributed to climate and irrigation withdrawals that support crop production. However, despite decades of effort, knowledge gaps remain in understanding the relative influence of drought and crop production on groundwater levels at the continental scale. Here, utilizing empirical observations, we simultaneously track how long-term trajectories of groundwater levels, crop production of seven crops, and drought have evolved over time, and then integrate these observations with a causality-based attribution framework to unravel the relative impact of drought and crop production on groundwater levels across the contiguous United States (CONUS). We find a dominant pattern of …

Exploring Biostimulant Efficacy Under Limited Fertilizer And Water In Utah's Watermelon Production, Evan Christensen, Milena Maria Tomaz De Oliveira, Prakriti Nepal, Youping Sun

Plants, Soils, and Climate Faculty Publications

The western U.S. has recently experienced some of the driest conditions on record, and Utah has been in a multi-year drought (2019-2023) that affected the agricultural sector, including vegetable producers. While vegetables are not a primary agricultural crop in Utah, they are still an important part of the horticultural economy with 763 farms growing 6,138 acres. As the fourth largest acreage vegetable crop in Utah (almost 10% of the acreage) watermelon and related crops in the gourd family Cucurbitaceae (nearly 36% of total vegetable acreage) are important to vegetable growers. Watermelon is a water-intensive crop and requires an adequate supply …

Impact Of Climate Change On North Central Texas, Diana K. T. Hansen

Earth & Environmental Sciences Dissertations - Archive

ABSTRACT

IMPACT OF CLIMATE CHANGE ON

NORTH CENTRAL TEXAS

Diana Kay Thomas Hansen, Ph.D.

The University of Texas at Arlington, 2025

Supervising Professor: Arne M.E. Winguth

The North Central Texas region is a rapidly expanding metropolitan area. One of the largest climate hazards that will affect human health in this region are extended heat waves and heavy precipitation. This study will examine how these hazards will change in response to climate change and the impact to human health due to weather extremes in a changing climate.

Coupled Model Intercomparison Project (Phase 6) simulations were used to evaluate future projected temperature …

Groundwater Pumping Impacts On Stream Depletion In Humboldt County, Ca: Integrating Analytical Models And Field Data, Andy Hans Heise

Cal Poly Humboldt theses and projects

This study addresses the significant concern of stream depletion from groundwater pumping in Humboldt County, CA. The objective of this study is to develop an analytical model for estimating stream depletion and integrating field data into model parameters.

The methodology involved conducting a field study near three operating wells by a stream, installing stream gages upstream and downstream of the wells, and recording pumping rates and schedules for two of the wells. The third well’s pumping data was synthetically generated, for privacy concerns of the well owner. The StreamDepletR package was used for estimating depletion rates in a stream in …

Karst Hydrologic Memory Supplements Streamflow During Dry Periods In Snow-Dominated, Mountainous Watersheds, Hyrum Tennant, Bethany T. Neilson, Devon Hill, Dennis L. Newell, James P. Evans, Seohye Choi, James P. Mcnamara, Nathaniel Ashmead, Tianfang Xu

Geosciences Faculty Publications

Analysis of PRISM and SNOTEL station data paired with USGS streamflow gage data in the western United States shows that, in snow-dominated mountainous watersheds, streamflow regimes differ between watersheds with karst geology and their non-karst neighbours. These carbonate aquifers exhibit a spectrum of flow paths encompassing karst conduits, including large fractures or voids that transmit water readily to springs and other surface waters, and matrix flow paths through soils, highly fractured bedrock, or porous media bedrock grains. A well-connected karst aquifer will discharge a large portion of its accumulated precipitation to surface water via springs and other groundwater flow paths …

Drought Pearl Millet- An Unpalatable Enigma, D J. Minson, J B. Hacker, M Shimojo, P Stuart, J Slatter

IGC Proceedings (1977-2023)

After planting in late 1989 there were many reports that Nutrifeed was unpalatable to cattle, sheep and horses. Seventy­five properties were visited where unpalatability was common, a questionnaire was distributed and samples of forage and soil were analysed. Forty-six properties reported unpalatability but on the other 29, pearl millet was palatable. Unpalatability developed only when forage grown on soil high in available nitrogen was subjected to a shortage of water. Unpalatable forage was dark green, contained more than 3S g N/kg DM and was often low in phosphorus, After rain or irrigation the new growth was usually palatable but stock …

Photosynthesis And Water Relations Of A C4 And A C3 Grass Under Doubled Carbon Dioxide, D Nie, M B. Kirkham, E T. Kanemasu

IGC Proceedings (1977-2023)

The objective of this project was to determine during an entire season the photosynthetic rate and water potential of a C3 grass (Kentucky bluegrass, Poa pratensis L.) and a C4 grass (big bluestem, Andropogon gerardii Vitman) grown with 2 levels of CO2 (ambient or twice ambient) and 2 water levels (field capacity or no water added). Elevated CO2 increased the photosynthetic rate of Kentucky bluegrass by an average of 76%. During mid-season (11 June-16 July), photosynthetic rate of high-water big bluestem with ambient CO2 was about the same as that of low-water big bluestem with doubled CO2• Under both water …

Adaptation Of Sainfoin Cultivars And Lucerne To Water Stress, S R. Mir Hosseini, P D. Kemp, D J. Barker, J Hodgson

IGC Proceedings (1977-2023)

Sainfoin ( Onobrychis viciifolia Scop.) is of particular interest as a pasture crop because it is a productive legume in dry areas but does not induce bloat in ruminant animals. In this study 3·sainfoin cultivars (Fakir, Melrose and 035) and l lucerne (Medicago saliva L.) cultivar Grasslands Oranga were compared during a drying phase when water was withheld once; flowering began. A randomised complete block design with 4 replicates' was used. Transpiration rate (Tr) declined as volumetric soil water content (VSWC) was reduced. Stomata! resistance (Rs) increased and relative ivater content (RWC) decreased when VSWC decreased. Critical VSWC for …

Physiological Response Of White Clover Genotypes To Water Deficit, D J. Barker, J R. Caradus, M T. Mcmanus

IGC Proceedings (1977-2023)

Three plants from each of 2 white clover (Trifolium repens L.) cultivars, Grasslands Kopu and a breeding line selected from germplasm of Syrian origin, were grown in large pots of soil and physiological characteristics measured during a continuous drying phase of 18-37 days. By the end of the experiment, leaf water potential was -2.5 MPa, gravimetric soil water content was 13% (considerably lower than -1.5 MPa), and leaf relative water content was 60%. A 91- fold increase in leaf praline concentration indicated that water stress had altered plant metabolism. Differences in the rate of soil drying occurred between eultivars, but …

Forecasting Annual Drought Conditions For Arid And Semi-Arid Rangelands, C L. Hanson, J R. Wight

IGC Proceedings (1977-2023)

Long-term weather forecasts (>14 days) have improved, but still lack accurate enough information to be valuable; thus, drought forecasts must be based on historical records and calculated probabilities of occurrence. The use of regression techniques to investigate linear dependence between current and preceding years' precipitation or forage yield is illustrated. A 3-state Markov process is used to determine relationships between below-average, average and above­average consecutive annual herbage yields, and winter and spring precipitation amounts. Methods for using natl/ml resource simulation models to forecast ecosystem components such as herbage production, runoff, and erosion with their associated probabilities of occurrence are …

Analysis Of Drought-Flood Abrupt Alternation Events And Their Impacts In Kenya, Betty Makena

School of Natural Resources: Dissertations, Theses, and Student Research

Drought-Flood Abrupt Alternation (DFAA) is a compound disaster event that refers to the abrupt shift of extreme drought events to extreme floods resulting in exacerbated impacts on already vulnerable communities and hindering their coping abilities. This study aimed to analyze drought-flood abrupt alternation events and their impacts in Kenya. The first chapter aimed to understand historical drought events in the Greater Horn of Africa and their impacts, while drawing comparisons with the recent 2020-2022 drought period, referred to as the ‘triple dip La Niña’. Datasets used in this study include the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS), Normalized …

Spatiotemporal Plasticity In Reproductive Readiness And Recruitment Of Ichthyoplankton Of Invasive Silver Carp Along A Western Invasion Front, Jessi L. Urichich

School of Natural Resources: Dissertations, Theses, and Student Research

Individuals of invasive species at the edge of their invasion distribution may exhibit enhanced reproductive capacity and phenotypic plasticity leading to accelerated range expansion. Environmental conditions in highly fluctuating environments at distribution edges may either promote or hinder such reproductive readiness and phenotypic plasticity. Dynamic habitat conditions and periodic disturbances experienced in prairie streams, such as drought (e.g., low-flow, high water temperatures), may potentially reduce suitable spawning environments and ichthyoplankton recruitment of invasive Silver Carp, potentially slowing range expansion or enabling management strategies that reduce abundance in the absence of a reproducing population. Female Silver Carp batch fecundity, Gonadosomatic Index …

Carbohydrate Reserves Of Perennial Grasses: Effect Of Drought And Defoliation Intensity, S P. Boschma, M J. Hill, J M. Scott, J J. Lutton

IGC Proceedings (1977-2023)

The carbohydrate reserves of six perennial grasses were measured during exposure to drought and defoliation over spring-summer and summer-autumn seasons. Of the six species assessed, tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) had the highest level of reserves while wallaby grass (Danthonia richardsonii) had the lowest levels. The results indicate that during the spring-summer period drought intensity had a greater effect on plant reserves than defoliation intensity. However, defoliation had a greater effect on reserves during the summer-autumn period. It is suggested that tiller reserves may be most affected when drought is …

Assessment And Prediction Of Meteorological Drought Using Machine Learning Algorithms And Climate Data, Khalid En-Nagre, Mourad Aqnouy, Ayoub Ouarka, Syed Ali Asad Naqvi, Ismail Bouizrou, Jamal Eddine Stitou El Messari, Aqil Tariq, Walid Soufan, Wenzhao Li, Hesham El-Askary

Mathematics, Physics, and Computer Science Faculty Articles and Research

Monitoring drought in semi-arid regions due to climate change is of paramount importance. This study, conducted in Morocco’s Upper Drâa Basin (UDB), analyzed data spanning from 1980 to 2019, focusing on the calculation of drought indices, specifically the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) at multiple timescales (1, 3, 9, 12 months). Trends were assessed using statistical methods such as the Mann-Kendall test and the Sen’s Slope estimator. Four significant machine learning (ML) algorithms, including Random Forest, Voting Regressor, AdaBoost Regressor, and K-Nearest Neighbors Regressor, were evaluated to predict the SPEI values for both three …

Investigating The Drought Sensitivity Of Intermontane-Basin Groundwater Systems In Western Montana Using Standardized Drought Indices, Daniel Buckley

Graduate Theses & Non-Theses

Drought is a worldwide phenomenon, and many metrics have been developed to help monitor and understand drought. In this study, the drought sensitivity of two different western Montana intermontane-basin groundwater systems were analyzed: the Bitterroot Valley and the Gallatin Valley. Different standardized meteorological drought indices, namely, the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI), were compared against the Standardized Groundwater level Index (SGI) to better understand groundwater sensitivity to meteorological forcing. The SPI and SPEI were computed using precipitation and reference evapotranspiration data from the gridMET dataset. Groundwater level data from the Montana Bureau of Mines …

The Interaction Between Root Distribution And Pasture Growth During Water Deficit, D J. Barker, N Dymock

IGC Proceedings (1977-2023)

Quantification of water-limited pasture growth is of interest in agriculture since it allows prediction of impaired animal production during drought, and is the basis for scheduling irrigation. Experimental work on two dairy pastures 25 km south-west of Palmerston North, New Zealand found 50% of root mass was in the top 2.3 cm of soil. Soil moisture was, similarly, not uniformly distributed down the soil profile and dried most rapidly in the top 20†cm of soil. Leaf appearance rate was more strongly correlated with water status nearer the soil surface (r = 0.52 & 0.63 for 0-5 & 10-15 cm depth, …

Response To Drought Of White Clover Lines Selected For Different Stolon Morphologies, H D. Karsten, J R. Caradus, D R. Woodfield

IGC Proceedings (1977-2023)

White clover (Trifolium repens L.) lines were selected from within large and small-leaved cultivars of Grasslands Kopu and Grasslands Tahora, respectively, for long or short internodes, and for high or low branching frequency from plants grown in sun and shade (50% full sunlight). Lines were compared for drought tolerance in a perennial ryegrass (Lolium perenne L.) sward in boxes. Prior to imposing drought branching frequency selections did not differ in branching frequency, although the low branching frequency selection had a higher percentage of rooted nodes. After an imposed drought treatment sun-selected lines grew better than shade-selected lines relative …