<p>Tropical Cyclones (TCs) intensity and frequency are expected to be impacted by climate change. Despite their destructive potential, these phenomena, which can produce heavy precipitation, are also an important source of freshwater. Therefore any change in frequency, seasonal timing and intensity of TCs is expected to strongly impact the regional water cycle and consequently the freshwater availability and distribution. This is critical, due to the fact that freshwater resources in the US are under stress due to the population growth and economic development that increasingly create more demands from agricultural, municipal and industrial uses, resulting in frequent over-allocation of water resources. </p><p>In this study we concentrate on monitoring the impact of hurricanes and tropical storms on vegetation activity along their terrestrial tracks and investigate the underlying physical processes. To characterize and monitor the spatial organization and time of recovery of vegetation disturbance in the aftermath of major hurricanes over the entire southeastern US, a remote sensed framework based on MODIS enhanced vegetation index (EVI) was developed. At the SE scale, this framework was complemented by a water balance approach to estimate the variability in hurricane groundwater recharge capacity spatially and between events. Then we investigate the contribution of TCs (season totals and event by event) to the SE US annual precipitation totals from 2002 to 2011. A water budget approach applied at the drainage basins scale is used to investigate the partitioning of TCs' precipitation into surface runoff and groundwater system in the direct aftermath of major TCs. This framework allows exploring the contribution of TCs to annual precipitation totals and the consequent recharge of groundwater reservoirs across different physiographic regions (mountains, coastal and alluvial plains) versus the fraction that is quickly evacuated through the river network and surface runoff. </p><p>Then a Land surface Eco-Hydrological Model (LEHM), combining water and energy budgets with photosynthesis activity, is used to estimate Gross Primary Production (GPP) over the SE US The obtained data is compared to AmeriFlux and MODIS GPP data over the SE United States in order to establish the model's ability to capture vegetation dynamics for the different biomes of the SE US. Then, a suite of numerical experiments is conducted to evaluate the impact of Tropical Cyclones (TCs) precipitation over the SE US. The numerical experiments consist of with and without TC precipitation simulations by replacing the signature of TC forcing by NARR-derived climatology of atmospheric forcing ahead of landfall during the TC terrestrial path. The comparison of these GPP estimates with those obtained with the normal forcing result in areas of discrepancies where the GPP was significantly modulated by TC activity. These areas show up to 10% variability over the last decade.</p> / Dissertation

Irrigation practices in the Rincon Valley and Mesilla Basin of the Lower Rio Grande have evolved over the last century into a complex setting of transboundary conjunctive use. Three major water users have surface and groundwater appropriation rights regulated by compact, treaty, and operating rules and agreements. The analysis of complex relationships between supply/demand components and the effects of surface-water and groundwater use requires an integrated hydrologic model to track all of the use and movement of water. Models previously developed for the region relied on a priori estimates of net irrigation flux or externally-calculated landscape water budgets. This study instead utilizes a MODFLOW model with the Farm Process (MF-FMP), which directly couples the surface-water and groundwater regimes through simulation of landscape processes. This allows the assessment of stream-aquifer interactions in the context of fulfilling irrigation demands with variable supplies of surface water allotments and supplemental groundwater pumping. MF-FMP also simulates direct uptake of groundwater by crops, an important utility for modeling a region with significant acreage dedicated to pecan orchards, a phreatophytic crop. The abilities and limitations of this new model are explored through scenario simulations meant to estimate streamflow depletions caused by historic pumping levels.

Στον ελληνικό χώρο, για έναν μεγάλο αριθμό λεκανών δεν υπάρχουν διαθέσιμες μετρήσεις απορροής, γεγονός που καθιστά δύσκολη την υδρολογική τους προσομοίωση για τον προσδιορισμό των συνιστωσών του υδρολογικού ισοζυγίου. Μια τέτοια περίπτωση αποτελούν οι λεκάνες απορροής των ποταμών του Πείρου και του Παραπείρου. Στους ποταμούς αυτούς κατασκευάζεται ένα σύστημα έργων που αποτελείται από ένα φράγμα εκτροπής στη θέση Βαλμαδούρα στον ποταμό Πείρο, έναν ταμιευτήρα στη θέση Αστέρι στον Παραπείρο και έναν συνδετικό αγωγό. Στόχος της κατασκευής των έργων αυτών αποτελεί η κάλυψη των υδρευτικών αναγκών της πόλης των Πατρών, της Βιομηχανικής Περιοχής και των κοινοτήτων της Β.Δ. Αχαϊας. Στη μελέτη των έργων αυτών (Υ.ΠΕ.ΧΩ.Δ.Ε., 1997) ο υπολογισμός του υδρολογικού ισοζυγίου στις λεκάνες που αντιστοιχούν στις θέσεις των έργων βασίστηκε σε απλοποιητικές παραδοχές. Συγκεκριμένα θεωρήθηκε ότι το νερό αποθηκεύεται μόνο στην εδαφική ζώνη και δεν γίνεται διάκριση ανάμεσα σε επιφανειακή και υπόγεια απορροή. Στην παρούσα εργασία για τον ακριβή και αναλυτικό προσδιορισμό των συνιστωσών του υδρολογικού ισοζυγίου χρησιμοποιήθηκε το υδρολογικό μοντέλο βροχής–απορροής ENNS (Nachtnebel, 1993), η χρήση του οποίου απαιτεί την εύρεση τιμών των παραμέτρων που υπεισέρχονται στις εξισώσεις των διαδικασιών που περιγράφουν το μοντέλο. Λόγω ελλείψεως μετρήσεων απορροής για τις λεκάνες του Πείρου και του Παραπείρου, για την εύρεση των τιμών των παραμέτρων του μοντέλου εφαρμόστηκε μια μεθοδολογία διερεύνησης της υδρολογικής ομοιότητας των δύο λεκανών με άλλες λεκάνες, για τις οποίες υπάρχουν διαθέσιμες μετρήσεις απορροής. Πιο συγκεκριμένα χρησιμοποιήθηκαν οι λεκάνες απορροής του Γλαύκου στον Νομό Αχαϊας, του Αχελώου που αντιστοιχεί στην θέση του φράγματος της Μεσοχώρας, του ποταμού Ερύμανθου, παραποτάμου του Αλφειού και του ποταμού Myakka στην Florida των Η.Π.Α.. Η διαδικασία που ακολουθήθηκε είναι η εξής: Αρχικά πραγματοποιείται η ρύθμιση του μοντέλου για τις τέσσερις λεκάνες για τις οποίες υπάρχουν μετρήσεις απορροής με στόχο (α) να βρεθούν οι τιμές των παραμέτρων που επηρεάζουν το αποτέλεσμα της προσομοίωσης και (β) να διαπιστωθεί το εύρος διακύμανσης των τιμών αυτών των παραμέτρων. Λόγω του σημαντικού εύρους διακύμανσης αυτών των παραμέτρων, πραγματοποιείται η κατάταξη των λεκανών του Πείρου, του Παραπείρου και των τεσσάρων λεκανών, για τις οποίες υπάρχουν διαθέσιμες μετρήσεις απορροής, σύμφωνα με κάποιους φυσιογραφικούς και κλιματικούς παράγοντες που επιλέχθησαν, ως προς την αναμενόμενη επιφανειακή απορροή. Στη συνέχεια, για τις λεκάνες για τις οποίες υπάρχουν διαθέσιμες μετρήσεις απορροής γίνεται έλεγχος εάν οι τιμές των παραμέτρων του μοντέλου είναι συμβατές με την κατάταξη των λεκανών σύμφωνα με τους φυσιογραφικούς και κλιματικούς παράγοντες. Επειδή προκύπτει ότι αυτό δεν συμβαίνει, πραγματοποιείται επαναρρύθμιση του μοντέλου αναζητώντας συνδυασμούς παραμέτρων, οι οποίοι να επαληθεύουν την κατάταξη των λεκανών. Τέλος με βάση τα αποτελέσματα της διερεύνησης της υδρολογικής ομοιότητας των λεκανών επιλέγονται οι τιμές των παραμέτρων του μοντέλου για την υδρολογική προσομοίωση των λεκανών του Πείρου και του Παραπείρου. Τα αποτελέσματα που προέκυψαν από την υδρολογική προσομοίωση του Πείρου και του Παραπείρου με την χρήση του μοντέλου συγκρίθηκαν με τα αποτελέσματα της μελέτης του Υ.ΠΕ.ΧΩ.Δ.Ε. (Μάρτιος 1997). Τα συμπεράσματα που προκύπτουν από την παρούσα εργασία είναι τα εξής: (α) Από την διερεύνηση της υδρολογικής ομοιότητας των λεκανών του Πείρου και του Παραπείρου με τις λεκάνες του Γλαύκου, του Ερύμανθου, της Μεσοχώρας και του ποταμού Myakka, Η.Π.Α. διαπιστώθηκε ότι η επαναρρύθμιση του μοντέλου που πραγματοποιήθηκε για τις τέσσερις λεκάνες, για τις οποίες υπαρχουν μετρήσεις απορροής, οδήγησε σε βελτίωση των αποτελεσμάτων της ρύθμισης (μείωση των αποκλίσεων της μετρημένης και προσομοιωμένης απορροής). Επίσης, επειδή ο λόγος της επιφανειακής απορροής προς την βροχή για τις τέσσερις λεκάνες επαληθεύει την κατάταξη σύμφωνα με τους φυσιογραφικούς και κλιματικούς παράγοντες, προκύπτει ότι η διαδικασία που ακολουθήθηκε αποτελεί μια δυνατότητα αντιστοίχισης των παραμέτρων του μοντέλου σε κριτήρια που προκύπτουν από αυτούς τους παράγοντες. (β) Από την σύγκριση των αποτελεσμάτων της μελέτης του Υ.ΠΕ.ΧΩ.Δ.Ε. με τα αποτελέσματα του μοντέλου αποδεικνύεται ότι το μοντέλο δίνει πιο ρεαλιστικές τιμές για τις συνιστώσες του υδρολογικού ισοζυγίου των λεκανών του Πείρου και του Παραπείρου από την μελέτη. Οι λόγοι είναι ότι (α) σύμφωνα με την κατάταξη των λεκανών βάσει των φυσιογραφικών και κλιματικών παραγόντων οι λεκάνες του Πείρου και του Παραπείρου παρουσιάζουν υδρολογική ομοιότητα με την λεκάνη του Γλαύκου, για την οποία το μοντέλο δίνει μια ρεαλιστική προσέγγιση της συνολικής απορροής (άμεσης και βασικής) και (β) η βασική απορροή που υπολογίστηκε με το μοντέλο παρουσιάζει πολύ μικρότερη μεταβλητότητα στον χρόνο έναντι της άμεσης απορροής λόγω της αποθηκευτικής ικανότητας του εδάφους. (γ) Από τα αποτελέσματα της υδρολογικής προσομοίωσης των λεκανών του Πείρου και του Παραπείρου με την χρήση του μοντέλου προκύπτει ότι τα ποσοστά της άμεσης απορροής προς την βροχόπτωση των λεκανών του Πείρου και του Παραπείρου σύμφωνα με το μοντέλο δεν ήταν τα αναμενόμενα, παρόλο που τα αποτελέσματα του μοντέλου κρίθηκαν ικανοποιητικά. Οι πιθανοί λόγοι είναι κάποια μειονεκτήματα που παρουσιάζει η μεθοδολογία διερεύνησης της υδρολογικής ομοιότητας των λεκανών και τα οποία κρίνεται ότι εάν ληφθούν υπόψη μπορούν να οδηγήσουν σε βελτίωση της μεθόδου. / In Greece, there is a significant number of ungauged basins, for which the hydrologic simulation is not possible and as a result calculating the components of the water balance is infeasible. The basins of the rivers Peiros and Parapeiros were selected as a case-study. These rivers are involved in a current project; the construction of a diversion dam in the position Valmadoura of Peiros River, a reservoir in the position Asteri of Parapeiros River and a conjection pipe. The aim of this project is to support the water supply of the city of Patras, the Industrial Region and the communities of the North-west Achaias. The study of this project conducted by the Hellenic Ministry of Environment, Physical Planning and Public Works in 1997 deals with the calculation of the water balance in these basins, based on simplified principles, assuming that the water is stored in the soil layer and there is no separation of the total runoff in surface flow and base flow. In the present study, the use of the rainfall-runoff model ENNS (Nachtnebel, 1993) allowed the exact and analytical quantification of the water balance. The use of this model requires the estimation of a number of parameters involved in the governing equations of the model. The lack of runoff measurements in Peiros and Parapeiros basins preclude the determination of the required parameters. A study of the hydrologic similarity of these two basins with a number of gauged basins gave solution to the problem. The chosen basins are: (a) Glaukos River basin in the prefecture of Achaias, (b) Mesoxora basin, a sub-basin of Acheloos River, (c) Erymanthos basin, a sub-basin of Alfeios River and (d) Myakka River basin, Florida of U.S.A. The procedure adopted is divided in the following steps: Firstly, the model ENNS was established for the basins mentioned previously in order to determine (a) the value of the parameters affecting the simulation result and (b) the range of their values. The significant variation led to the classification of the six basins, according to physiographic and climatic characteristics. The criterion used in the classification is the expected surface runoff to the amount of rainfall. Secondly, a compatibility check between the values of the parameters of the model and the basins classification was performed. The unsatisfying result compelled the reestablishement of the model for the four gauged basins with an aim to obtain the appropriate parameters in accordance with the basins classification. Finally, the values of the ENNS parameters, regarding Peiros and Parapeiros basins, were derived from the study of the hydrologic similarity of the basins. The results of the hydrologic simulation of Peiros and Parapeiros were compared to the results of the study conducted by the Hellenic Ministry of Environment, Physical Planning and Public Works in 1997. The conclusions of the present study are: (a)The setup of the ENNS model taking into account the hydrologic similarity study of the six basins improved the results of the model (decrease of the deviations between the measured and simulated discharge values). Moreover the ratio of the surface runoff to the rainfall for the four gauged basins verifies the basins classification. Hence, a satisfying degree of correlation between the model parameters and the physiographic and climatic basin characteristics, is obtained. (b)Comparing the obtained results to those of the Hellenic Ministry of Environment, Physical Planning and Public Works study in 1997, the present model gives a more realistic view of the water balance. The reasons are: (a) according to the basins classification, Peiros and Parapeiros basins are similar to Glaukos basin, for which the model gives a realistic approach of the total runoff (surface and base flow) and (b) the base flow calculated by the model shows a smaller variability, contrary to the surface flow due to the storage capacity of the soil. (c)The results of the hydrologic simulation of Peiros and Parapeiros basins showed that the percentage of the surface runoff to the amount of rainfall for the two basins is not compatible to the classification (smaller than 36.5% of Glaukos basin). However, the results of the model are satisfactory (accordance of the annual simulated values of actual evapotranspiration to the values calculated using the Turc method). The possible reasons are some disadvantages in the basins hydrologic similarity study that must be taken into consideration in order to improve the method.

Project Completion Report, OWRT Project No. A-086-ARIZ / Agreement No. 14-34-0001-8003, Project Dates: 10/01/77-9/30/78 / Acknowledgement: The work upon which this report is based was supported by funds provided by the State of Arizona and the United States Department of Interior, Office of Water Research and Technology as authorized under the Water Resources Act of 1964. / From the Introduction: "The research work under this contract has been conducted by graduate student David B. Dunbar and summarized in his M.S. thesis entitled "Analysis of a Parameter Estimation Technique for Linear Hydrologic Systems Using Monte Carlo Simulation" submitted to the Department of Hydrology and Water Resources, University of Arizona, Tucson, in 1981. The present report is a brief summary of Mr. Dunbar's thesis." David Dunbar's thesis is available at: http://arizona.openrepository.com/arizona/handle/10150/191728 / The primary accomplishment of this research has been demonstrating the power of the deconvolution technique developed by Neuman and de Marsily (1976) in dealing with noisy rainfall- runoff records of short duration. Such records are encountered in arid environments where rainfall often occurs in short isolated bursts and the data are measured with a considerable margin of error. Our research work consisted of superimposing known noise on synthetic rainfall- runoff data and examining the ability of the Neuman -de Marsily deconvolution method to estimate the correct impulse response of the system when the data include only a single storm event. Approximately 50 Monte Carlo simulation runs were performed for each of three different noise models considered in our work. The results clearly demonstrated that the deconvolution model leads to reliable estimates and can be used with confidence in the presence of realistic noise levels. In addition to the Monte Carlo simulation tests and their analysis, certain improvements were introduced into the original deconvolution technique. In particular, the original version of the technique required that the hydrologist exercise subjective judgement in choosing the "best" solution for the deconvolution problem from a large number of admissible solutions. Our new method of selecting the "best" result is based on a comparative analysis of residuals and is more reliable than the earlier subjective approach. The improved method has been applied to real as well as synthetic rainfall -runoff data.

Research Project Technical Completion Report / Office of Water Research and Technology Project A-031-ARIZ / Annual Allotment Agreement No. 14-31-0001-5003 / FCST Research Category VII-C; OWRT Problem Area: 10 / Project Duration June 1971 to June 1975 / No publication date on item; publication date from catalog. / The Arizona Water Information System (AWIS) was developed for storage and retrieval of water resources data and for dissemination of water resources information pertaining to the State of Arizona. Collectively, the AWIS system contains a number of distinct elements. The Activity File is a listing of water resource activities and projects dating from 1961, which can be accessed by keywords or by agency to retrieve abstracts and information on approximately 1,000 projects; the file recently was updated and additional projects covered in a regional program pertaining to the Lower Colorado River Basin portions of Arizona, California, and Nevada. A bimonthly Arizona Water Resources News Bulletin and a companion Project Information Bulletin were initiated under this project and will be continued as a cooperative effort of the Arizona Water Commission and the University of Arizona Water Resources Research Center and Office of Arid Lands Studies. A cassette-tape pilot series on Arizona water trends also was produced and evaluated for use potential, which appears favorable. A western state conference on water information dissemination, sponsored by this project and OWRT, was held in Phoenix in 1973, to discuss the above kinds of activities in the several states and the possibilities for cooperative regional activities. The capability for interactive hydrologic data processing, utilizing the DEC -10 computer system at the University of Arizona, was developed in 1974 with the support of the Arizona Water Commission (AWC). Ground-water and quality-of-water data furnished by AWC have been stored progressively in the system, and are retrievable by remote terminal through telephone hookup, by quarter- township grid location or by drainage basin. Routine inquiries can be answered rapidly, or more complex retrievals can be made as desired.

The aim of the research undertaken in this dissertation was to use medium-range to seasonal precipitation forecasts for hydrologic applications for catchments in the core North American Monsoon (NAM) region. To this end, it was necessary to develop a better understanding of the physical and statistical relationships between runoff processes and the temporal statistics of rainfall. To achieve this goal, development of statistically downscaled estimates of warm season precipitation over the core region of the North American Monsoon Experiment (NAME) were developed. Currently, NAM precipitation is poorly predicted on local and regional scales by Global Circulation Models (GCMs). The downscaling technique used here, the K-Nearest Neighbor (KNN) model, combines information from retrospective GCM forecasts with simultaneous historical observations to infer statistical relationships between the low-resolution GCM fields and the locally-observed precipitation records. The stochastic nature of monsoon rainfall presents significant challenges for downscaling efforts and, therefore, necessitate a regionalization and an ensemble or probabilistic-based approach to quantitative precipitation forecasting. It was found that regionalization of the precipitation climatology prior to downscaling using KNN offered significant advantages in terms of improved skill scores.Selected output variables from retrospective ensemble runs of the National Centers for Environmental Predictions medium-range forecast (MRF) model were fed into the KNN downscaling model. The quality of the downscaled precipitation forecasts was evaluated in terms of a standard suite of ensemble verification metrics. This study represents the first time the KNN model has been successfully applied within a warm season convective climate regime and shown to produce skillful and reliable ensemble forecasts of daily precipitation out to a lead time of four to six days, depending on the forecast month.Knowledge of the behavior of the regional hydrologic systems in NAM was transferred into a modeling framework aimed at improving intra-seasonal hydrologic predictions. To this end, a robust lumped-parameter computational model of intermediate conceptual complexity was calibrated and applied to generate streamflow in three unregulated test basins in the core region of the NAM. The modeled response to different time-accumulated KNN-generated precipitation forcing was investigated. Although the model had some difficulty in accurately simulating hydrologic fluxes on the basis of Hortonian runoff principles only, the preliminary results achieved from this study are encouraging. The primary and most novel finding from this study is an improved predictability of the NAM system using state-of-the-art ensemble forecasting systems. Additionally, this research significantly enhanced the utility of the MRF ensemble forecasts and made them reliable for regional hydrologic applications. Finally, monthly streamflow simulations (from an ensemble-based approach) have been demonstrated. Estimated ensemble forecasts provide quantitative estimates of uncertainty associated with our model forecasts.

Railroad bridges and culverts in the United States are often subject to extreme floods, which have been known to washout sections of track and ultimately lead to derailments. The potential for these events is particularly high in the western U.S. due to the lack of data, inadequate radar coverage, and the high spatial and temporal variability of storm events and terrain. In this work, a hydrologic model is developed that is capable of effectively describing the rainfall-runoff relationship of extreme thunderstorms in arid and semi-arid regions. The model was calibrated and validated using data from ten storms at the semi-arid Walnut Gulch Experimental Watershed. A methodology is also proposed for reducing the amount of raingages required to provide acceptable inputs to the hydrologic model, and also determining the most appropriate placement location for these gages. Results show that the model is capable of reproducing peak discharges, peak timings, and total volumes to within 22.1%, 12 min, and 32.8%, respectively. Results of the gage reduction procedure show that a decrease in the amount of raingages used to drive the model results in a disproportionally smaller decrease in model accuracy. Results also indicate that choosing gages using the minimization of correlation approach that is described herein will lead to an increase in model accuracy as opposed to selecting gages on a random basis.

No description available.

<p>The research was driven by a need to increase the knowledge base concerning wetland ecological responses, as well as to identify and evaluate the factors driving the functioning of the Franschhoek Trust Wetland. An ecohydrological study was undertaken in which vegetation cover, depth to groundwater, water and soil chemistry were monitored at 14 sites along three transects for a 12 month period. The parameters used include temperature, pH, electrical conductivity (EC), sodium, potassium, magnesium, calcium, iron, chloride, bicarbonate, sulphate, total nitrogen, ammonia, nitrate, nitrite and phosphorus. T-tests and Principal Component Analysis (PCA) were used to analyze trends and to express the relationship between abiotic factors and vegetation.</p>

This thesis evaluates regional hydrology using output from the Canadian Regional Climate Model (CRCM 4.1) and examines changes in the hydrological processes over the Churchill River Basin (CRB) by employing the Variable Infiltration Capacity (VIC) hydrology model. The CRCM evaluation has been performed by combining the atmospheric and the terrestrial water budget components of the hydrological cycle. The North American Regional Reanalysis (NARR) data are used where direct observations are not available. The outcome of the evaluation reveals the potential of the CRCM for use in long-term hydrological studies. The CRCM atmospheric moisture fluxes and storage tendencies show reasonable agreement with the NARR. The long-term moisture flux over the CRB was found to be generally divergent during summer. A systematic bias is observed in the CRCM precipitation and temperature. A quantile-based mapping of the cumulative distribution function is applied for precipitation adjustments. The temperature correction only involves shifting and scaling to adjust mean and variance. The results indicate that the techniques employed for correction are useful for hydrological studies. Bias-correction is also applied to the CRCM future climate. The CRCM bias-corrected data is then used for hydrological modeling of the CRB. The VIC-simulated streamflow exhibits acceptable agreement with observations. The VIC model's internal variables such as snow and soil moisture indicate that the model is capable of simulating internal process variables adequately. The VIC-simulated snow and soil moisture shows the potential of use as an alternative dataset for hydrological studies. Streamflow along with precipitation and temperature are analyzed for trends. No statistically significant trend is observed in the daily precipitation series. Results suggest that an increase in temperature may reduce accumulation of snow during fall and winter. The flow regime may be in transition from a snowmelt dominated regime to a rainfall dominated regime. Results from future climate simulations of the A2 emission scenario indicate a projected increase of streamflow, while the snow depth and duration exhibit a decrease. Soil moisture response to future climate warming shows an overall increase with a greater likelihood of occurrences of higher soil moisture.