• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 36
  • 31
  • 17
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 114
  • 114
  • 25
  • 25
  • 18
  • 16
  • 15
  • 12
  • 12
  • 11
  • 10
  • 10
  • 10
  • 9
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Space-time modelling of seasonal soil moisture for improved crop production – the case of the Guinea savannah region, Ghana

Nketia, Kwabena Abrefa 03 July 2020 (has links)
No description available.
102

Scaling methods of leakage correction in GRACE mass change estimates revisited for the complex hydro-climatic setting of the Indus Basin

Tripathi, Vasaw, Groh, Andreas, Horwath, Martin, Ramsankaran, Raaj 18 April 2024 (has links)
Total water storage change (TWSC) reflects the balance of all water fluxes in a hydrological system. The Gravity Recovery and Climate Experiment/Follow-On (GRACE/GRACE-FO) monthly gravity field models, distributed as spherical harmonic (SH) coefficients, are the only means of observing this state variable. The well-known correlated noise in these observations requires filtering, which scatters the actual mass changes from their true locations. This effect is known as leakage. This study explores the traditional basin and grid scaling approaches, and develops a novel frequency-dependent scaling for leakage correction of GRACE TWSC in a unique, basin-specific assessment for the Indus Basin. We harness the characteristics of significant heterogeneity in the Indus Basin due to climate and human-induced changes to study the physical nature of these scaling schemes. The most recent WaterGAP (Water Global Assessment and Prognosis) hydrology model (WGHM v2.2d) with its two variants, standard (without glacier mass changes) and Integrated (with glacier mass changes), is used to derive scaling factors. For the first time, we explicitly show the effect of inclusion or exclusion of glacier mass changes in the model on the gridded scaling factors. The inferences were validated in a detailed simulation environment designed using WGHM fields corrupted with GRACE-like errors using full monthly error covariance matrices. We find that frequency-dependent scaling outperforms both basin and grid scaling for the Indus Basin, where mass changes of different frequencies are localized. Grid scaling can resolve trends from glacier mass loss and groundwater loss but fails to recover the small seasonal signals in trunk Indus. Frequency-dependent scaling can provide a robust estimate of the seasonal cycle of TWSC for practical applications such as regional-scale water availability assessments. Apart from these novel developments and insights into the traditional scaling approach, our study encourages the regional scale users to conduct specific assessments for their basin of interest.
103

Untersuchungen zur Variabilität der Ausbildung hyperdermaler Wasserspeichergewebe unter Berücksichtigung variegater Periklinalchimären

Faßmann, Natalie 09 June 2008 (has links)
Die Arbeit ist in drei Teile untergliedert: Die Struktur "Hypodermales Wasserspeichergewebe" wird unter anatomischen, ökomorphologischen und evolutionsbiologischen Gesichtspunkten betrachtet. Die Anwesenheit eines farblosen Hypoderms erschwert bei der Musteranalyse variegater Periklinalchimären die Bestimmung der Konstitution der L2. Variegate Periklinalchimären mit Hypodermbildung wurden auf die Möglichkeiten der Bestimmung der L2 hin untersucht. Es werden verschiedene Entstehungsformen von maskierenden Mustern und die noch nicht beschriebenen Ringzellen vorgestellt, die den Idiotyp der L2-bürtigen Schicht anzeigen können. Ringzellen sind die Zellen, die im Bereich der Schließzellen an den substomatären Interzellularraum grenzen. Sie bilden dabei einen Ring um die Schließzellen, der im Flächenschnitt zu erkennen ist. Hypodermale Wasserspeichergewebe sind hauptsächlich bei tropischen Arten verbreitet. Die xeromorphe Struktur kommt sowohl bei den epiphytischen Bromelien als auch bei den hygromorphen Schattenpflanzen des tropischen Regenwaldes vor. Die beiden Selektionsfaktoren Trockenheit und Lichtintensität werden als mögliche Einflussfaktoren auf die Hypodermbildung diskutiert. Beispiele dafür, dass der Faktor Licht auch einen modifikativen Einfluss auf die Differenzierung der Hypodermzellen zu haben scheint, werden vorgestellt. Die Struktur "Hypodermales Wasserspeichergewebe" ist sowohl bei Monokotylen als auch Dikotylen gleichermaßen verbreitet. Es wird daher vermutet, dass es sich um eine analoge Struktur handelt, die mehrmals voneinander unabhängig zu verschiedenen Zeiten bei verschiedenen Arten entstanden ist. Innerhalb einer Gruppe verwandter Arten konnte sie mithilfe der Homologiekriterien als homolog eingestuft werden. / This paper contains three different issues: The structure "hypodermal water storage tissue" is considered from the anatomical, the ecomorphological and evolutionary aspect. Because hypodermal layers are non-green, it is difficult to make a pattern analysis of variegated periclinal chimeras and to determine the constitution of L2. Variegated periclinal chimeras with hypodermal layers were examined to the possibilities of determining L2. Different origins of masking patterns and the non-yet described ring cells are presented. Both structures are able to show the L2-genotype. Ring cells are those cells bordering the intercellular space near the stomata. In a cut parallel to the surface the ring built by ring cells is seen. The hypodermal water storage tissue is mainly distributed among tropical species. The xeromorphic structure occurs both to the epiphytic bromeliads and to the hygromorphic shadow plants of the tropical rainforest. The environmental factors humidity and solar radiation are discussed as possible influences on the development of hypodermal layers. Examples for the apparent modifying influence of solar radiation on the development of hypodermal cells are presented. The structure "hypodermal water storage tissue" occurs both to monocots and dicots. That indicates that it is an analogues structure and that it evolved several times independent of each other in different species. Among a group of nearly related species it could be classified by the aid of the criteria of homology as a homologues structure.
104

Time-Related Changes in Water Quality of Stock Tanks of Southeastern Arizona

Wallace, D. E., Schreiber, H. A. 20 April 1974 (has links)
From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / This study attempts to determine the water quality changes in stock tanks and what factors are instrumental in the changes, and to assess the effects of the changes. Algal growth was the most prominent change taking place in the tanks with time. Little change in the water chemistry was noted until just before the tanks dried up. As algae died, ions tied up by the algae were released to the water, causing an increase in concentration of many of the nutrients. In order to determine the impact of various factors on algal growth, the data from eight stock tanks were analyzed by stepwise linear regression. Although 20 variables were used in the complete analysis, six variables were associated with 56.3 percent of the variance: time (since first sampling), total n, potassium, pH, inflow (recharge to the tanks), and hco3 concentration. Time and total n explained 51.3 percent of the variance, and potassium increased the variance to 52.8 percent. The pH reversed the relative positions of time and total n, with total n becoming dominant. The last two factors, inflow and hco3 were negative (resulting in a decrease in algal population) and increased the coefficient of variance to 56.3 percent.
105

Water Resources of the Inner Basin of San Francisco Volcano, Coconino County, Arizona

Montgomery, E. L., DeWitt, R. H. 20 April 1974 (has links)
From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / The inner basin is a collapse and erosional feature in San Francisco Mountain, an extinct volcano of late Cenozoic age, which lies approximately eight miles north of flagstaff, Arizona. The main aquifer's coefficient of transmissibility is approximately 14,000 gallons per day per foot and the storage coefficient was 0.08. Aquifer boundaries increased rates of drawdown of water levels in the inner basin well field. Inner basin springs which issue from perched reservoirs are not affected by pumpage of inner basin wells. Recharge is greater than the average yield from springs and wells in the basin which has an average of 8,000 acre-feet of water in storage in the principal aquifer. A large amount of water is lost from the inner basin aquifer system via leakage into underlying fractured volcanic rocks. It is believed that a part of this water could be intercepted by pumpage from a well constructed in the interior valley.
106

Structural Relations Determined from Interpretation of Geophysical Surveys: Woody Mountain Well Field, Coconino County, Arizona

Scott, Phyllis K., Montgomery, E. L. 20 April 1974 (has links)
From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / The Coconino Sandstone of Permian age is the principal aquifer for the Woody Mountain well field, a source of municipal water for the City of Flagstaff. Wells of highest yield are located where the frequency of occurrence of faults is greatest and where the principal aquifer is down-faulted. The locations and displacements of all but the most prominent faults cannot be determined using conventional geologic mapping techniques because relatively undeformed Late Cenozoic basaltic lavas cover the faulted Paleozoic rock terrain. Approximately 3,500 feet of Paleozoic sedimentary rocks, which have little magnetic effect and which have a density of approximately 2.4, comprise most of the stratigraphic section in the well field. The basalt cover is strongly reversely magnetized and has a density of approximately 2.7. Changes in thickness of the basalt cover cause changes in the geomagnetic and gravitational field strength. Analysis of data from geomagnetic and gravity surveys was used to delineate boundaries and thicknesses of blocks of basalt which fill down -faulted areas. The correlation coefficient (r² = 0.96) for plots of known thicknesses of basalt versus complete Bouguer anomaly supports use of gravity data to estimate displacement of down -faulted blocks.
107

Preliminary Investigations of the Hydrologic Properties of Diatremes in the Hopi Buttes, Arizona

Scott, Kenneth C., Edmonds, R. J., Montgomery, E. L. 20 April 1974 (has links)
From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / Diatremes of Late Pliocene age in the Hopi Buttes area of Arizona are becoming increasingly important sources of groundwater to the Indian nations. These volcanic vent structures are prime sources of groundwater because sedimentary formations in the Hopi Buttes area yield only limited amounts of water or yield poor quality water. Diatremes act as traps for groundwater and some have yielded moderate amounts of good quality water to wells. Surface geologic investigations and analysis of drillers' logs indicate that structural relationships and diatreme lithology provide a means to project the hydrologic properties of the vent. Diatremes most suitable for groundwater development should have a diameter greater than one half mile, should contain volcanic tuff and breccia at its center, and should be fractured from collapse. Lava flows covering diatremes reduce recharge from sheet wash or from ephemeral stream flow. Data from geomagnetic and gravity surveys will be analyzed to determine its suitability for predicting subsurface size, shape, and lithology of the diatreme. The integration of geophysical and surface geologic data will reveal the total geometry of the structure enabling the most accurate appraisal of the hydrologic properties of the diatreme.
108

The Compartmented Reservoir: Efficient Water Storage in Flat Terrain Areas of Arizona

Cluff, C. B. 15 April 1978 (has links)
From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona / The compartmented reservoir is presented as an efficient method of storing water in areas of Arizona having a relatively flat terrain where there is a significant water loss through evaporation. The flat terrain makes it difficult to avoid large surface- area-to-water-volume ratios when using a conventional reservoir. Large water losses through evaporation can be reduced by compartmentalizing shallow impervious reservoirs and in flat terrain concentrating water by pumping it from one compartment to another. Concentrating the water reduces the surface-area-to-water-volume ratio to a minimum, thus decreasing evaporation losses by reducing both the temperature and exposure of the water to the atmosphere. Portable, high-capacity pumps make the method economical for small reservoirs as well as for relatively large reservoirs. Further, the amount of water available for beneficial consumption is usually more than the amount of water pumped for concentration. A Compartmented Reservoir Optimization Program (CROP-76) has been developed for selecting the optimal design configuration. The program has been utilized in designing several systems including several in Arizona. Through the use of the model, the interrelationship of the parameters have been determined. These parameters are volume, area, depth, and slope of the embankment around each compartment. These parameters interface with the parameters describing rainfall and hydrologic characteristics of the watershed. The water -yield model used in CROP-76 requires inputs of watershed area, daily precipitation and daily and maximum depletion. In addition, three sets of seasonal modifying coefficients are required either through calibration or estimated by an experienced hydrologist. The model can determine runoff from two types of watersheds, a natural and /or treated catchment. Additional inputs of CROP-76 are the surface water evaporation rate and the amount and type of consumptive use.
109

Kotelny na biomasu / Biomass boiler room

Egerle, Dušan January 2013 (has links)
The aim of this project is heating and warm water preparation for apartment block in Choceň (Pardubice region). Apartment block has three aboveground heated floors and one underground unheated floor. The heat source is gasifying firewood boiler or pellet boiler which is at the same time used for water heating but only in the winter time. The other parts of the year the solar collectors are installed and used for water heating. The heat source is located in detached room with its own access, in boiler room.
110

Omvandla Malmö till en "svampstad"? : En studie om sponge city-konceptet / Transform Malmö into a sponge city? : A study about the sponge city-concept

Dracic, Melisa January 2021 (has links)
Förekomsten av vattenrelaterade problem som extrem nederbörd, översvämningar, torka och vattenbrist kommer att öka i urbana områden till följd av de globala klimatförändringarna. Sponge city-konceptet är ett urbant dagvattenhanteringssystem som lanserades i Kina och syftar till att förbättra vattenhanteringen i städer genom att återställa stadens kapacitet att absorbera, infiltrera, lagra och rena vatten. Den här studien syftade till att undersöka om sponge city-konceptet hade kunnat implementeras i Malmö genom att besvara frågeställningen ” Vilka möjligheter respektive hinder finns det för Malmö att implementera sponge city-konceptet?”. Genom en systematisk litteraturstudie och innehållsanalys i kombination med det teoretiska ramverket som baserades på konceptet sårbarhet för klimatförändringar visade resultatet på att det både finns en del möjligheter men också hinder. Det huvudsakliga hindret som identifierades är att en stor del av marken i Malmö består av täta moränleror vilket utgör ett hinder för de infiltrationsåtgärder som ingår i sponge city-konceptet. Några möjligheter som identifierades är att sponge city-konceptet kan minska känsligheten för skada som uppstår i förhållande till exponeringsnivån, samt att Malmös anpassningskapacitet är relativt hög. På grund av att den här studien enbart undersökte specifika fysiska/miljömässiga aspekter inom sponge city-konceptet krävs däremot fler studier som tar hänsyn till fler aspekter om en implementering av konceptet skulle bli aktuell. / The occurrence of water related problems such as extreme precipitation, floods, drought and water scarcity will increase in urban areas as a result of global climate change. The sponge city-concept is an urban stormwater system launched in China and aims to improve the water management in cities by restoring the city’s capacity to absorb, infiltrate, store and purify water. This study aimed to investigate if the sponge city-concept could be implemented in Malmö by answering the question “What possibilities and obstacles exist for Malmö to implement the sponge city-concept?”. Through a systematic literature review and content analysis in combination with the theoretical framework, which was based on the concept climate change vulnerability, the results showed that there are some possibilities but also obstacles. The main obstacle that was identified is that the ground in Malmö largely consists of dense moraines which forms an obstacle for the infiltration measures that are included in the sponge city-concept. Some possibilities that were identified is that the sponge city-concept can decrease the sensitivity to harm that occurs in relation to the exposure level but also that Malmö’s adaptation capacity is relatively high. However, because this study only investigated specific physical/environmental aspects within the sponge city-concept, more studies that consider more aspects are required if an implementation of the concept would become prevailing.

Page generated in 0.0747 seconds