Meadows in the Sierra Nevada Mountains are an important ecological resource that have degraded in quality and distribution due to several environmental and anthropogenic stressors. The encroachment of conifers beyond forest meadow ecotones is largely responsible for the decline of meadow habitat throughout the past century. Currently, there is little research that quantifies the hydrologic response to removal of conifers encroaching meadows in terms of implicating successful meadow restoration. This study has implemented a before after control intervention (BACI) study design to determine the hydrologic response associated with the removal of conifers from a historic meadow encroached by conifers. The primary goals of this research were to: (1) establish a method to evaluate the weekly water balance of an encroached meadow before and after conifer removal (restoration) (2) characterize the hydrology of an encroached meadow and a nearby control meadow prior to restoration (3) assess the effectiveness of electrical resistivity tomography in improving the spatial interpretation of subsurface hydrology on our study site. A water budget approach was developed to quantify the hydrology of a control and study meadow (Marian Meadow) before and after restoration. In order to determine weekly changes in groundwater depth, 14 Odyssey water level capacitance instruments were installed to a 1.5 meter depth in PVC wells. In order to quantify changes in soil moisture storage, 14 soil moisture probes were installed to a ~1 ft (30 cm) depth. Both sets of instruments were installed using a spatially balanced random sampling approach. Electrical resistivity tomography was conducted on both meadows on three separate dates during: September 9-10 2013, May 5 2014 and September 6-7 2014. A method to quantify runoff from a stream that drains Marian Meadow (Marian Creek) was also established. The Priestley Taylor model was used to estimate daily evapotranspiration from both meadows. Electrical resistivity tomography improved the spatial interpretation of groundwater recharge and facilitated the use of a recession curve analysis to model groundwater recharge when the water table receded beyond instrument detection depths. Electrical resistivity also demonstrated a change in hydrologic characteristics across a forest –meadow ecotone. Analysis of the pre-removal hydrologic characteristics from September 2013 to December 2014 indicates that Marian Meadow may be a favorable candidate for restoration (in terms of hydrology). On Marian Meadow, volumetric soil moisture was higher than the Control Meadow from May-November 2014. Sufficient soil moisture in the summer months is thought to be critical to the maintenance of endemic meadow flora. The water table depth on Marian Meadow and the Control Meadow was similar throughout the analysis period, but Marian Meadow had a shallower water table during the summer months. The Control Meadow had near surface groundwater during short periods from February-April 2014 and December 2014. If conifer removal from Marian Meadow causes an increase in seasonal volumetric soil moisture and a decrease in seasonal groundwater depth, an augmented version of the stable hydrologic system already present on Marian Meadow may result in hydrologic conditions more favorable to meadow restoration.

The U.S. Green Building Council (USGBC) is the developer of the Leadership in Energy and Environmental Design (LEED™) green building scoring system. On first inspection of LEED points, few address water efficiency. However, water management encompasses other points beyond the Water Efficiency (WE) category. In general, the industry is apt to take a somewhat compartmentalized approach to water management. The use of alternative water sources or the reuse of wastewater significantly complicates the water budget picture. A total water management systems approach, taking into consideration water from various sources, both inside and outside the building, should be implemented in order to devise a strategy for optimal reduction of potable water consumption and wastewater generation. Using the STELLA software to create an integrated building water management (IBWM) model provides stakeholders with a tool to evaluate potential water savings under dynamic conditions for a specific project site. Data collection for IBWM model calibration also shows that water consumption trends are unique to each project, and using LEED assumptions about water usage can overestimate or underestimate potential water savings.

I estimated patterns of shorebird abundance and species diversity in the Colorado River Delta and Upper Gulf of California wetlands in order to determine the relative contribution of intertidal wetlands and non-tidal anthropogenic wetlands to support shorebird habitat use. Species richness varied from 15 to 26 species among sites and 29 species were detected across sites. Density during the peak migration month was higher at the anthropogenic wetland Cienega de Santa Clara (mean = 168 ind/ha, 95% C.I. 29-367), and the intertidal Golfo de Santa Clara (mean = 153 ind/ha, 95% C.I. 17-323). Anthropogenic wetlands (playa and lagoons) supported high abundance of shorebirds along with intertidal wetlands in the Colorado River Delta (mudflats). In contrast, intertidal wetlands farther south on the Sonoran Coast presented lower abundance but higher diversity of shorebird, likely as a result of the higher diversity of habitats (rocky shore, sandy beach, estuary). I modeled water management scenarios for the Cienega in order to determine the response of the dominant vegetation (southern cattail, Typha domingensis Pers.) and the area of the outflow pool below the marsh to different scenarios of water management. The model indicates that if the inflow rate is reduced below the current 4-5 m³s⁻¹ the vegetated area of the Cienega that supports habitat for marsh birds would decrease in proportion, as would the area of the outflow pool in the Santa Clara Slough identified previously as shorebird habitat. Increases in salinity will also reduce the vegetated area due to the low salt tolerance of T. domingensis. In winter about 90% of inflow water exits the Cienega into the Santa Clara Slough due to low evapotranspiration contributing to inundate areas that are used by wintering and migrating shorebirds. Lastly, I explored the feasibility of using Vegetation Indices (NDVI and EVI) to model Yuma Clapper Rail detections in the Cienega de Santa Clara as well as the effects of adding other habitat variables and the presence of fire events in the performance of linear models based on NDVI. Both NDVI and EVI were positively related to the Yuma Clapper Rail detections. The relationship was weak to moderate, but significant (P<0.001), which suggests other factors besides the vegetation condition play an important role in the bird distribution pattern. A model including all the variability among years was a better predictor of the rails detected per transect, than models for fire and non-fire years. We did not find a significant effect from adding habitat features (water % or vegetation %), and we recommend to include variables at both microhabitat level and landscape level, relevant before and during the breeding season in order to increase the explanatory power of models.

Master of Science / Agronomy / Robert Aiken / Xiaomao Lin / Productivity of water-limited cropping systems can be reduced by untimely distribution of water as well as cold and heat stress. The research objective was to develop relationships among weather parameters, water use, and grain productivity to produce production functions to forecast grain yields of grain sorghum and winter wheat in water-limited cropping systems. Algorithms, defined by the Kansas Water Budget (KSWB) model, solve the soil water budget with a daily time step and were implemented using the Matlab computer language. The relationship of grain yield to crop water use, reported in several crop sequence studies conducted in Bushland, TX; Colby, KS and Tribune, KS were compared against KSWB model results using contemporary weather data. The predictive accuracy of the KSWB model was also evaluated in relation to experimental results. Field studies showed that winter wheat had stable grain yields over a wide range of crop water use, while sorghum had a wider range of yields over a smaller distribution of crop water use. The relationship of winter wheat yield to crop water use, simulated by KSWB, was comparable to relationships developed for four of five experimental results, except for one study conducted in Bushland that indicated less crop water productivity. In contrast, for grain sorghum, experimental yield response to an increment of water use was less than that calculated by KSWB for three of five cases; for one study at Colby and Tribune, simulated and experimental yield response to water use were similar. Simulated yield thresholds were consistent with observed yield thresholds for both wheat and sorghum in all but one case, that of wheat in the Bushland study previously mentioned. Factors in addition to crop water use, such as weeds, pests, or disease, may have contributed to these differences. The KSWB model provides a useful analytic framework for distinguishing water supply constraints to grain productivity.

At the end of the 20th century, the combination of climatic and anthropogenic events resulted in hyper salinity conditions in the coastal wetland Ciénaga Grande de Santa Marta (CGSM), Colombia. Although salinity concentrations are generally related to the type and quantity of water entering and exiting a wetland and to its internal hydrological dynamics, there have been no up to date hydrological studies on the CGSM. Here we show how a water budget can be used as a first-order of approximation to describe the CGSM's hydrology, despite data limitations. We collected hydroclimatic data to calculate and analyze the fluxes of water entering and exiting CGSM and their corresponding uncertainties. We find that the water budget is mostly affected by the precipitation regime, a result connected to studies of regional El Niño/La Niña effects. Scenario analyses show that contribution of freshwater from the streams coming down from the Sierra Nevada Mountain Range on the eastern side of CGSM is currently larger than that of the channels draining from Magdalena River to the west, in contrast to the general focus on the western side. However, Monte Carlo simulations suggest that the eastern freshwater inflow is insignificant in affecting the hydrological response of CGSM. These results outline the need to (1) increase understanding of the internal connectivity and circulation of CGSM and (2) further investigate the effect of agriculture on the eastern side of CGSM.

Meadows are crucial components to larger river watersheds because of their unique hydrologic and ecological functions. Due to climate change, over grazing, and fire suppression, conifer encroachment into meadows has accelerated. In some western regions, nearly half of all meadow habitat has been loss due to conifer encroachment. Restoration of these hydrologic systems requires tree removal. Many studies exist that address the issue of conifer encroachment in montane meadows, however, few studies focus on the role that conifer removal plays on the encroaching meadow. Furthermore, few studies exist that document the hydrologic change from conifer removal and further restoration steps, if any, to take after the removal. The overall research goal is to understand the efficacy of removal of encroached conifers from an encroached meadow (Marian Meadow) for successful meadow restoration. The objectives of this study are to determine (i) quantify the meadow hydrology following removal of encroached conifers, (ii) determine if forest tree removal adjacent to the meadow influences the meadow’s hydrology, and (iii) test three common revegetation techniques for a formerly encroached montane meadow.. Marian Meadow is in Plumas County, CA at an elevation of 4,900 feet. This 45-acre meadow enhancement project is part of a 2,046-acre timber harvest plan implemented by the Collins Pine Company. Soil moisture sensors at one foot below the ground and water table depth sensors at four feet below ground were installed in Marian Meadow and a control meadow in September 2013, with additional soil moisture sensors at three-foot depth installed August 2015. The removal of encroaching conifers from Marian Meadow occurred in June 2015. Electrical Resistivity Tomography (ERT) was used to determine maximum water table depths and climatic variables were measured from a weather station as inputs for the water budget. A groundwater recession curve equation was used to model water table depths between water table depth sensor measurements and ERT measurements. A general linear model was used to determine any statistical significant difference in soil moisture and water table depths prior to and after conifer removal. Revegetation plots were installed at the start of the 2017 growing season to determine the establishment rate for three different techniques (BARE, WOOD, and EXISTING) and three different species of meadow plant. Technique BARE, which removes approximately 10 cm of top soil and disperses seed was statistically significant, yielding the highest population count. Another growing season data collection and control plot is required to draw further conclusions and recommendations. The water balance indicated that the majority of Marian Meadow and the Control Meadow’s water storage can be attributed to precipitation and not upland sources. This hydrologic characteristic is common in dry meadows. The statistical analysis indicated that measured water table depths increased on average by 0.62 feet following conifer removal. The first year following restoration and the second year following restoration yielded statistically significantly different water levels than pre-restoration water levels. The third year following restoration is inconclusive until the end of the 2018 WY data set is available. On average, soil moisture increased by 6.43% following conifer removal and was statistically significantly different in all three post restoration years when compared to pre-restoration volumetric soil moisture content. Additionally, growing season (April through September) water table depths indicated that meadow vegetation communities could be supported in Marian Meadow following conifer removal. The removal of conifers from an encroached meadow appears to promote soil moisture and water table depth conditions indicative of a meadow and meadow plant community types.

This PhD is focused on the eastern region of Colombia and the practical development of this work was composed of three stages that lead to three different articles which are the main body of this study. The first stage was focused on a systematic review of the climate characteristics over the last decades at eastern Colombia including a data survey and evaluation of the historical available data records. In the second stage, the Statistical Downscaling Model (SDSM) was used as a tool for downscaling meteorological data statistically over four representative water districts at the eastern side of Colombia. Here, data from the two Global Climate Models CanESM2 and IPSL-CM5A-MR, which are part of the CMIP5-project have been used to project future maximum and minimum temperature, precipitation and relative humidity for the periods 2021–2050 and 2071–2100. For both models, the Representative Concentration Pathways RCP2.6 and RCP8.5 were considered, representing two different possible future emission trajectories and radiative forcings. In the third stage, the results of the second stage together with the hydrological model BROOK90 and complementary data were utilized to determine the future changes in the water balance components in the previously selected four water districts in Eastern Colombia.

Forest fires demand personnel and financial resources. GIS can monitor ecological conditions that promote forest fire ignition. Visual representations of fire potential in the state could aid in staging firefighting personnel and equipment. This paper details the creation of a descriptive fire potential model for the Southeastern Fire District of Mississippi. The model includes the variables of fuels, ignition based on road density, and climate. No descriptive model of fire potential exists for Mississippi that includes a climate variable. The main objective of this research was to examine the influence of the dynamic climate variable on the model. Estimates of two water budgets were created to identify areas where evaporation exceeded precipitation and raised the potential for fires to occur. The study supported previous findings of road density as a significant variable for fire potential and validated the use of a climate variable in the model describing fire potential.

The design of wetlands to replace those lost to development requires quantitative understanding of the wetland water budget in order to estimate the amount of water available to the wetland over time. Many methods exist to estimate each component of the wetland water budget. In this study, monthly values of the water budget components namely, precipitation, runoff, evapotranspiration, and groundwater seepage were calculated using a water budget model and compared to on-site field measurements for a wetland in Manassas, Prince William County, VA. The monthly precipitation estimated from a weather station 32.18 km from the site differed from the on-site values by as much as 2.9 times. Runoff estimates calculated by the Soil Conservation Service (SCS) method using antecedent moisture condition (AMC) II underpredicted runoff for every month by as high as 100 percent compared to the on-site measured runoff. The choice of AMC greatly affected the SCS runoff estimates. Runoff was the dominant water budget component at the Manassas wetland. The evapotranspiration (ET) estimates using the Thornthwaite method either over or underestimated ET when compared to ET calculated from diurnal cycles of the water table in the wetland. Groundwater seepage losses were calculated using Darcy's equation with an assumed hydraulic gradient of one, and with gradients measured with nested piezometers. Seepage losses at the Manassas wetland were negligible. Overall, the water budget model provided conservative estimates of the available water in the wetland during the 10-month period of observation. / Master of Science

Dans les environnements semi-arides la ressource en eau est soumise aux irrégularités du climat. Les eaux de surface sont très irrégulièrement réparties dans le temps et dans l'espace. Le cumul annuel des précipitations est généralement faible et les évènements sont rares et intenses, causant des crues violentes et une forte érosion. Les eaux souterraines constituent souvent la principale ressource pérenne utilisable et elles sont largement mises à contribution. Pour pallier aux conséquences néfastes de ces régimes hydrologiques, des projets de grands barrages ont été menés dans ces zones pour favoriser le stockage d'eau. Paradoxalement, la mise en place de ces ouvrages crée un déficit en eau dans certaines zones en induisant des pertes par évaporation et la diminution de la recharge des nappes. Des situations complexes nouvelles sont ainsi créées, nécessitant des modes de gestions adaptés. En Tunisie centrale, le bassin versant du Merguellil fournit un exemple de processus hydrologique profondément modifié par la construction d'un grand barrage. Le bassin revêt une importance stratégique pour la région. Il alimente la plaine de Kairouan qui constitue le plus fort potentiel de développement agricole du pays et dont la nappe alluviale est surexploitée. Les écoulements intermittents de l'oued rechargeaient autrefois la nappe phréatique de la plaine. Le barrage d'El Haouareb construit en 1989 bloquant désormais les écoulements de surface, la recharge se produit plus en amont via le socle calcaire fissuré de l'ouvrage. Cette modification du fonctionnement hydrologique entraine une perte significative d'eau par évaporation et concentre la recharge à l'extrême amont de la plaine, au pied du barrage. Le but de cette thèse est d'identifier les mécanismes de recharge qui s'opèrent au niveau du seuil d'El Haouareb. L'infiltration depuis le lac de barrage a été quantifiée d'après le bilan hydrologique de la retenue et cet état de 56 % de perte par infiltration, 24 % de perte par évaporation, 14 % utilisés pour l'irrigation et 6 % relâchés depuis 1989. Le bilan a été fait à des pas de temps plus fin pour permettre de modéliser les entrées dans le système aquifère.L'identification des flux transitant à travers le seuil calcaire a été menée en croisant des approches hydrodynamiques (analyse du signal) et géochimiques (profils et chronique de CE et températures, chimie des ions majeurs, isotopes stables de la molécule de l'eau). La confrontation des différentes méthodes a permis de consolider les résultats et de pallier aux imperfections de certaines données de terrain dans un contexte hydrologique et hydrogéologique complexe. Un modèle simplifié de l'aquifère fracturé et un schéma de fonctionnement du seuil ont ainsi pu être établis, permettant d'anticiper l'évolution des mécanismes de recharge dans le bassin du Merguellil sous des contraintes climatiques futures. / In semi-arid environment, surface waters are unevenly distributed in time and space and particularly vulnerable. The total annual rainfall is generally low and the rain events are rare and intense, causing severe flooding and erosion. Therefore, the groundwater resource is widely exploited, often inducing overexploitation problems.To overcome the negative consequences of these hydrological regimes, large dam have been built to increase the water storage. These structures can paradoxically create a water deficiency in some areas by inducing evaporation losses and reducing aquifer recharge. In central Tunisia, the Merguellil catchment provides an example of hydrological processes profoundly changed by the construction of a large dam. The basin is of strategic importance for the region. It feeds the great agricultural plain of Kairouan which suffers f overexploitation for decades. Before the building of the El Haouareb dam, the Merguellil intermittent flows were the main source of recharge to the Kairouan plain aquifer. Dam El Haouareb built in 1989 now blocking surface runoff, recharge occurs further upstream through the cracked limestone base of the structure. This modification of the hydrological causes a significant loss of water by evaporation and concentrate recharge of the plain at the foot of the dam.The purpose of this thesis work is to identify the recharge mechanisms occurring at the threshold of El Haouareb. Infiltration from the lake was quantified calculating the water budget of the reservoir. The total water budget between 1989 and 2006 was made up by: infiltration 56%, evaporation 24%, abstraction 14% and dam releases 6%. Calculations had been conducted for smaller time scale to allow the quantification of the entries in the aquifer system.The identification of flows passing through the calcareous threshold was conducted by crossing hydrodynamic approaches (signal analysis) and geochemical (profiles and records of electrical conductivity and temperature, major ions, stable isotopes of the water molecule). The comparison of different methods helped to consolidate the results and to overcome the imperfections of some field data in a hydrological and hydrogeological complex context.A basic model and a simplified diagram of the El Haouareb aquifer have been established and allow anticipating the evolution of recharge in the Merguellil catchment under future climatic pressure.