Thesis (M.Sc. Agriculture (Soil Science)) -- University of Limpopo, 2021 / Woody plant encroachment results in the degradation of grasslands. It is defined here as the increase in density, cover and biomass of woody plants into formerly open grasslands, reducing grassland productivity. Globally, many arid and semi-arid savanna grasslands are affected by this land cover transformation which changes the vegetation structure by altering the ratio of woody plants relative to grass species and influences soil hydrology. In the existing literature there is limited information on the effects of woody plant encroachment on soil physical and hydrological properties, especially in savanna grasslands. This study quantified and compared the soil physical and hydrological properties in the topsoil and subsoil of open and woody plant encroached grassland sites located on two contrasting soil forms, namely Bainsvlei and Rensburg. To achieve this objective, the two soils were sampled at various depth intervals from dug soil profiles at both sites at Towoomba Research Station in Bela Bela, Limpopo Province, South Africa. Soil physical properties including bulk density, porosity and aggregate stability as well as hydrological properties (water retention and hydraulic conductivity) were determined from collected samples. Compared to open grassland, soil bulk density was 11% and 10% greater in the topsoil and subsoil, while porosity was respectively 6% and 9% lower in the topsoil and subsoil of woody plant encroached grassland for Rensburg soils. In Bainsvlei soil, there was a minimal increase and decrease in the soil bulk density and porosity, respectively. Soil aggregate stability increased by 38% in the subsoil of woody plant encroached grasslands in Rensburg soil, due to increasing clay content with depth. In Bainsvlei soil, the soil aggregate stability was 9% and 13% lower in the topsoil and subsoil of the woody plant encroached grasslands compared to open grassland. Furthermore, the results revealed that in both soils, there was lower soil water retention and hydraulic conductivity in the topsoil and subsoil layers of woody plant encroached grassland than in open grasslands. There were no significant differences observed for soil hydraulic conductivity in the Bainsvlei and Rensburg topsoil. The subsoil hydraulic conductivity decreased by 24% in Bainsvlei and 44% in Rensburg soils in the woody plant encroached grassland. The soil water retention (SWR) decreased with an increase in woody plants. Specifically, there was 25% and 42% decrease in SWR with woody plant encroachment in the topsoil and subsoil of Bainsvlei soil, respectively. The same trend was observed in the Rensburg soils with 50% and 19% decrease in SWR in the topsoil and subsoil, respectively. Overall, the results revealed that soil type and depth influenced soil physical and hydrological properties in the studied woody plant encroached savanna grassland. As such, interventions aimed at controlling woody plant encroachment need to factor in soil type and depth in the development of management practices tailored to improve the soil hydrology of savanna grasslands

The aim of diploma thesis is design and lay-out of high pressure pumping station with plunger pumps for splash of scales from slabs of hot-rolled. Theoretic (introduction) part of this thesis contain description of formation of scales and description of ways how it is possible remove these scales. And this part contains also explication of effect of water jet on solid material. The practical part of diploma thesis is focused on design of pumping station including of dimensioning of machinery. Part of this work is also technical documentation for proposed pumping station and specification of main machines and devices.

Purpose of this thesis is to make constructional modification of single-purpose pressing machine for Huisman Konstrukce, s.r.o. company. Present machine is non-operational and not enough powerful for present requests of workshop. Intended modifications are to describe present condition of machine, find present requirements and design simple modifications. All modifications are checked by calculations and sketched in shop drawings. There were also made alternative options of modification to show machine more versatile and automatic.

The subject of the thesis is to develop a simplified documentation of multipurpose reservoirs in the cadastral territory Třebařov. This thesis consists of the text, graphic and hydraulic calculations.

Climate change results to more extreme and frequent flood events that induce extra risk to flood protection structures such as levees. Thus, estimation of the probability of levee failure is of utmost importance when it comes to structural safety and flood risk assessment. This master thesis focuses on the estimation of the probability of levee failure owing to backward erosion at the foundation of the levee. For the estimation of the probability of failure three breach models of different complexity were developed and site-specified data were used from the Paglia river area and an assessment of the results followed. Besides the breach models, a 2-D hydraulic model was also built where breach scenarios were used to assess the associated flood risk. The results showed that the complexity of the breach model plays significant role to the estimated probability of failure. The simplest model estimated the lowest probability, while the complex the highest. Consequently, the associated to the complex model flood risk was higher than the other two. / Klimatförändringarna är ett allmänt problem som bland annat resulterar i ökad risk för extrema hydrologiska händelser. Av dessa extrema händelser är översvämningar bland de mest förekommande. För att tackla problemen med översvämningsriskerna används skyddsvallar som en av de vanligaste anläggningarna bland olika översvämningsskydd. Vid ett tillräckligt högt flöde kan dock den ökade belastningen på skyddsvallen orsaka att skyddsvallen havererar. En skyddsvall kan haverera på grund av flera fysikaliska fenomen, varav de vanligaste är inre erosion, otillräcklig släntstabilitet samt överspolning. Risken för att en skyddsvall havererar, det vill säga brottrisken, kan beräknas med olika metoder. Sannolikhetsbaserade metoder har nyligen växt fram som ett allt viktigare tillvägagångssätt. Det här examensarbetet handlar om brottsannolikhetsberäkningar för skyddsvallar i syfte att kartlägga översvämningsrisker. Arbetet fokuserar på fenomenet med inre erosion i skyddsvallars grundläggning. Det praktiska exemplet i examensarbetet studerar nybyggda skyddsvallar utmed den italienska floden Paglia längs en flodsträcka om 4,5 km mellan städerna Ciconia och Orvieto Scalo i regionen Umbria i centrala Italien. Ur ett hydrogeologiskt perspektiv karaktäriseras regionen av fint jordmaterial, med inslag av slutna akviferer. Sannolikhetsberäkningar med hjälp av ramverket för Monte Carlo-analys genomfördes för tre olika modeller för att beskriva inre erosion i skyddsvallarna till följd av ett 200-årsflöde. De tre olika numeriska modellerna kännetecknades av olika grad av komplexitet. Den enklaste modellen baserades på en metod av Mazzoleni et al. (2015) och tog endast hänsyn till skyddsvallens porositet. Den mellankomplexa modellen var baserad på metoden ifrån Khilar et al. (1985). Den mest komplexa modellen var tidsberoende och baserades på metoderna från Sellmeijer et al. (2011) och Scheuermann (2005), för att ta hänsyn till de två ömsesidigt beroende fenomenen bakåterosion, så kallad ”piping” och läckage, så kallat ”seepage”, vilka tillsammans ger upphov till inre erosion. Resultaten visar att graden av komplexitet i den numeriska modellen spelar en viktig roll när det gäller brottsannolikheten för skyddsvallars grundläggning. Den enklaste modellen beräknade en lägre brottsannolikhet än de andra två modellerna, och den mest komplexa modellen beräknade högst brottsannolikhet av de tre modellerna. Vidare visar resultaten på att några parametrar har en stor inverkan på brottsannolikheten. Dessa är bland annat partikeldiametern som påverkar skjuvhållfastheten i materialet, permeabiliteten, jordlagrets tjocklek under skyddsvallen samt strömningsvaraktigheten. Parametern strömningsvaraktighet kan endast beaktas i tidsberoende modeller, vilket är en av fördelarna med den mest komplexa modellen i denna studie. Förutom de numeriska brottsannolikhetsmodellerna byggdes en tvådimensionell hydraulisk modell upp för att kartlägga de resulterande översvämningsriskerna. Tre olika haveriscenarier studerades för att representera de tre brottsannolikhetsmodellerna. Dock visade det sig att den enklaste av de tre modellerna beräknade så låg brottsannolikhet att det inte var meningsfullt att studera de resulterande översvämningsriskerna enligt den enklaste brottsannolikhetsmodellen i den hydrauliska modellen. Av de två mer komplexa brottsannolikhetsmodellerna visade det sig att den mest komplexa av de två gav mer omfattande haverier i skyddsvallarna och dessutom haverier i flera av skyddsvallarna. Vidare gav den mest komplexa modellen upphov till högst vattennivåer bakom de havererade skyddsvallarna. Slutligen kan det nämnas att staden Scalo Orvieto är utsatt för en högre översvämningsrisk än staden Ciconia enligt resultaten i denna studie.

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<p>Flow-Accelerated Corrosion (FAC) is a pipe wall thinning mechanism affecting carbon steel piping systems in power generation plants. Mass transfer is the rate limiting factor, even though chemistry and materials determine the overall potential for FAC. Different localized thinning rates in back to back elbow configurations between the first and second elbow have been noted at nuclear power plants, and this difference depends on the length of pipe between the elbows, flow conditions, and the configuration of the back to back elbows (e.g. S, C, or out of plane). In this thesis, mass transfer measurements in back to back elbows arranged in an out of plane configuration under single and annular two-phase flow conditions are presented.</p> <p>The mass transfer measurements were performed using a wall dissolving technique with bend sections cast from gypsum. The diffusivity of gypsum in water is similar to the diffusivity of iron from the magnetite layer of carbon steel pipe in water, thus providing analogous mass transfer conditions to FAC in power generation plants. The wall dissolution of gypsum allows the surface roughness to develop due to the flow. The mass transfer is determined by passing water through the gypsum test sections in a flow loop system. The test sections are then sectioned into two halves to expose the worn surface. The surface topology is measured using a three dimensional laser scanner. The wear progression of the surface with time provides local mass transfer rates, locations of high mass transfer and local surface roughness.</p> <p>The single-phase flow experiments were performed at a Reynolds number of 70,000 for different lengths of pipe (0, 1, 2 and 5 pipe diameters) between the elbows. The mass transfer results show regions of higher mass transfer in the second elbow in comparison to the first el­­bow. The maximum mass transfer rate in the second elbow decreases when the length of the pipe between the elbows was increased from 0 to 5 pipe diameters. Surface features corresponding to flow streaks on the second elbow surface indicated swirling flow, and its strength decreases with increasing separation distance between the elbows. The surface roughness was found to be higher in the regions of high mass transfer and decreases with increasing elbow separation distance.</p> <p>The effect of air and water superficial velocities on the mass transfer for the bends with a separation distance of 0 pipe diameters was measured under two-phase air-water annular flow. In addition, the effect of separation distance of 0, 1 and 5 pipe diameters in length between the elbows was studied for one annular flow condition. The highest mass transfer was found on the outer wall of the first elbow for all cases. The maximum mass transfer in the second elbow was found to be approximately 60 percent of the maximum value in the first elbow, and was not affected significantly when the elbow separation distance was increased from 0 to 1 and 5 pipe diameters. The separation distance between the elbows did not affect the maximum mass transfer on the outer wall of the first elbow. The mass transfer increased with an increase in either the water or air superficial velocity, with the air velocity having a greater effect. The mass transfer enhancement factor relative to that in a straight pipe only increases significantly with increasing air superficial velocity. The roughness development in the pipe was modest, but increases significantly in the high mass transfer region of the first and second elbow.</p> / Master of Applied Science (MASc)

We studied piping plovers (Charadrius melodus Ord) on Assateague Island National Seashore, Maryland, during the 1988-1990 breeding seasons. The estimated breeding population declined from 25 pairs in 1988 to 14 pairs in 1990. Nest predation by red foxes (Vulpes vulpes) was high. Predator exclosures constructed around individual nests did not increase nest survival. Chick survival was higher in bay beach and island interior brood-rearing habitats than on the ocean beach. Our evidence supports the hypothesis that the availability of adequate food is driving the differences in survival observed among brood-rearing habitats. Chicks raised on the bay beach or island interior weighed more, had higher foraging rates, and spent a greater proportion of their time foraging than chicks reared on the ocean beach. Indices of invertebrate prey abundance indicated that insects were more abundant on the bay beach and island interior than on the ocean beach. Disturbance did not differ among brood-rearing habitats. Human disturbance was higher in 1990 than in previous years. Overall productivity was 0.71 chicks fledged/breeding pair, well below our estimate of the productivity needed to deter a population decline. Management efforts should focus on reducing nest predation and maintaining overwash access paths to high quality brood-rearing habitat. / Master of Science

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The southern bed of the ogallala aquifer is hydrologically isolated from all outside areas of recharge, requiring local precipitation for all natural recharge. Current withdrawals are so much greater than natural recharge that it appears that artificial recharge affords the only means of establishing at least a pseudo-balance. A number of observation wells were drilled at Texas Tech University, and subsequently capped until recharge water became available. The initial recharge was 2.5 af over 12 days, at a rate of 120 gpm for about the first day, after which 60 gpm was relatively constant. Approximately 1 month later, 1.2 af were recharged over 3 days at rates ranging over 140-90 gpm. It became evident that a cavity was present at the bottom of the hole being recharged. On a later recharge occasion, the cavity seemed to have enlarged. During a period of 2 years more than 28 af of surface runoff water have been recharged through the shallow hole with increases in recharge rates for each subsequent recharge period. The nature of this phenomenon and the cavities are not understood. This may represent the long sought after answer to recharge of the aquifer, but much more extensive research needs to be done.