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Vulnerability assessment of surface water supply systems due to climate change and other impacts in Addis Ababa, Ethiopia / Riskanalys av ytvattenförsörjning med avseende på klimatförändring och andra effekter i Addis Abeba, EtiopienElala, Daniel January 2011 (has links)
In Addis Ababa, Ethiopia, open reservoirs provide the majority of the drinking water. In the study present and future condition of these water sources and supplies were systematically assessed regarding water quantities. The study was done by reviewing municipal documents and accessing meteorological, hydrological and demographical data in Addis Ababa. 0%, 5% and 10% change in reservoir inflow/rainfall were used and projections for 2020 and 2030 were used to estimate future temperature and population sizes. The result indicated that supplied water quantity per capita from surface sources in Addis Ababa is likely to be reduced. Both climate and socio-economic related vulnerabilities were identified and the four following got the highest risk score: Increases in population, increased per capita water demand, overexploited land and increased distribution losses.At present the annual increase in population in Ethiopia is 4.4% and annual GDP increase is 7%, leading to a growing water demand in Addis Ababa. If the water supplies are not substantially increased the situation will lead to water scarcity. By 2020 water demand coverage will be 34% and by 2030 22%, compared with the current 50% coverage.Overexploited land was also identified as a major vulnerability due to the impact on catchment hydrology and distribution losses, caused by insufficient maintenance and replacement of aged pipes. At present 20% of the treated water is lost and it is likely to increase during the coming decades. However, the climate change induced rainfall variability is unlikely to cause large problems within the observed timeframe. Even with a 100 year drought 14% of the available water would be spill due to the limited reservoir capacity.To secure future water distribution Addis Ababa Water and Sewerage Authority (AAWSA) should build dams north of the Entoto ridge. They should also gain further understanding about and find appropriate measures for, highlighted vulnerabilities. A full vulnerability assessment should be done by AAWSA and they should consider implementing a „Water Safety Plan‟ for the whole water supply system.
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A process-based stable isotope approach to carbon cycling in recently flooded upland boreal forest reservoirsVenkiteswaran, Jason January 2002 (has links)
Reservoirs impound and store large volumes of water and flood land. The water is used for electricity generation, irrigation, industrial and municipal consumption, flood control and to improve navigation. The decomposition of flooded soil and vegetation creates greenhouse gases and thus reservoirs are a source of greenhouse gases. Reservoirs are not well studied for greenhouse gas flux from the water to the atmosphere. The FLooded Upland Dynamics EXperiment (FLUDEX) involves the creation of three experimental reservoirs in the upland boreal forest to study greenhouse gas and mercury dynamics. The balance of biological processes, decomposition, primary production, CH<sub>4</sub> oxidation and the nitrogen cycle in the reservoirs controls the greenhouse gas flux from the reservoir to the atmosphere. Understanding the importance and controlling factors of these processes is vital to understanding the sources and sinks of greenhouse gases within reservoirs. The carbon and oxygen dynamics near the sediment-water interface are very important to the entire reservoir because many processes occur in this area. Light and dark benthic chambers were deployed, side-by-side, to determine the benthic flux of DIC and CH<sub>4</sub> across the sediment-water interface and to determine the role of benthic photoautotrophs in benthic DIC, CH<sub>4</sub> and O<sub>2</sub> cycling. Benthic chambers have shown photoautotrophs use the decomposing soil, rocks and exposed bedrock as a physical substrate to colonize and the CO<sub>2</sub> produced by the decomposing soil as a carbon source since the delta<sup>13</sup>C-DIC value of the DIC added to light chambers is enriched relative to dark chambers and net photosynthesis rates are linked to community respiration. Benthic photoautotrophs consume 15-33% of the potential DIC flux into the water column. CH<sub>4</sub> produced by the decomposition of soils is partially oxidized by methanotrophs that use the photosynthetically produced oxygen. The delta<sup>13</sup>C-CH<sub>4</sub> values of the CH<sub>4</sub> added to light chambers is enriched relative to dark chambers and 15-88% of the potential CH<sub>4</sub> flux into the water column is oxidized. An isotope-mass budget for DIC and CH<sub>4</sub> is presented for each reservoir to identify the importance of processes on areservoir scale. Input of DIC to the reservoirs from overland flow can be important because concentration is greater and delta<sup>13</sup>C-DIC values are depleted relative to inflow from Roddy Lake. Estimates of total reservoir primary production indicate that 3-19% of the total DIC production from decomposition is removed by photoautotrophs. The carbon cycling in biofilm and the importance of periphytic primary production needs to be better understood. Dissolved delta<sup>13</sup>C-CH<sub>4</sub> values of CH<sub>4</sub> in reservoir outflow enriched 45-60permil, indicating that CH<sub>4</sub> oxidation was an important CH<sub>4</sub> sink within the reservoirs. Stable carbon isotope data indicates that the CH<sub>4</sub> in the bubbles is partially oxidized so the site of bubble formation is the upper portion of the flooded soil. The fraction of CH<sub>4</sub> converted to CO<sub>2</sub> in the FLUDEX reservoirs is similar to that of the wetland flooded for the Experimental Lakes Area Reservoir Project (ELARP). Approximately half of the dissolved CH<sub>4</sub> in the FLUDEX reservoirs was removedby CH<sub>4</sub> oxidation. The ebullitive flux of CH<sub>4</sub> from FLUDEX reservoirs is reduced 25-75% by CH<sub>4</sub> oxidation. The CH<sub>4</sub> flux to the atmosphere from peat surface of the ELARP reservoir became less oxidized after flooding: 91% to 85% oxidized. The floating peat islands of the ELARP reservoir were less oxidized than the peat surface. Similar to the CH<sub>4</sub> in the FLUDEX reservoirs, CH<sub>4</sub> in the ELARP peat islands was oxidized 56%. CH<sub>4</sub> oxidation is an important process because it reduces the global warming potential of the greenhouse gas flux since CO<sub>2</sub> is less radiatively active than CH<sub>4</sub>.
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Has the Redesign of Columbia Lake Improved Water Quality in Laurel Creek?Yu, Han January 2008 (has links)
Stormwater impoundments are one of many types of best management practices (BMP) designed and implemented to regulate water quantity and improve the quality of runoff from urban areas. Studies of water quality in urban impoundments have indicated that conventional designs are however, not very effective at removing solids and associated pollutants. Accordingly, many urban impoundments are being re-designed to improve downstream water quality. However, few studies have systematically monitored and quantified post-design water quality improvements of urban impoundments. This thesis examines changes in the water quality performance of an urban impoundment (Columbia Lake) in Waterloo, Ontario resulting from redesign of the lake for the pre-design period (2003 and 2004) and the post-design period (2006 and 2007). To achieve this goal, four years of water quality data collected at the inlet and outlet of Columbia Lake as part of the Laurel Creek Monitoring Program was measured. Water chemistry parameters included total phosphorus (TP), soluble reactive phosphorus (SRP), suspended solids (SS), dissolved oxygen (DO), pH and total dissolved solids (TDS). Inlet and outlet discharge (Q) were measured to determine the water retention time in the lake. Concentrations and loads of TP and SS for the post-design period (2006 and 2007) were compared to those for the pre-design period (2003 and 2004).
During the pre-design period (2003 and 2004), inflow TP concentrations ranged from 18 to 372 µg L-1 with an average (mean ± standard error) of 56±7 µg L-1, while outflow TP concentrations ranged from 37 to 266 µg L-1 with an average of 116±6 µg L-1. Post-design TP concentrations ranged from 10 to 124 µg L-1 with an average of 53±5 µg L-1 and from 14 to 147 µg L-1 with an average of 44±3 µg L-1 at the inflow and outflow, respectively. Pre-design SS concentrations ranged from 1.8 to 168.5 mg L-1 with a mean of 19.0±3.2 mg L-1 and from 4.0 to 194.7 mg L-1 with a mean of 66.6±4.7 mg L-1 at the inflow and outflow, respectively. Post-design SS concentrations varied from < 0.1 to 25.8 mg L-1 with an average of 8.5±0.8 mg L-1 and from < 0.1 to 42.5 mg L-1 with an average of 14.5±0.8 mg L-1 at the inflow and outflow, respectively.
Sedimentation/resuspension dominated the TP and SS transfer via Columbia Lake. Pre-design TP loads (log-transformed) strongly correlated with SS loads at the inflow and outflow (r = 0.661 and 0.777, p = 0.0001). These parameters were more strongly correlated during the post-design period (r = 0.794 and 0.915, r = 0.0001), which indicates that particulate P (PP) was a dominant fraction of TP and that the release of dissolved phosphorus (DP) from bottom sediments was considerably decreased following the redesign. No significant difference was observed between inflow and outflow SRP concentrations. Discharge strongly affected TP and SS loads at the inflow and outflow during the pre- and post-design periods (r > 0.79, p = 0.000 for all). After the redesign of Columbia Lake, the average net internal P loading rate decreased from 198% to 22% for TP. The primary factor influencing the observed decreased post-design TP and SS outputs was the removal of sediment from the lake. Bottom sediment removal and changes to the lake bathymetry reduced sediment resuspension and P desorption, which decreased the average net internal SS loading rate from 828% to 154%. The Columbia Lake Water Quality Model developed by Stantec Consulting Ltd. (2004) underestimated the post-design outflow TP and SS concentrations mainly because it did not include terms that account for factors such as bioturbation, wave induced resuspension and biological activity.
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Exploration of Potential Reservoir Hosts and Vectors of Leishmania in NicaraguaRaymond, Russell Wayne 15 May 2009 (has links)
Leishmaniasis is caused by infection with protozoan parasites within the genus
Leishmania and, in the New World, is transmitted by the bites of female sand flies
within the genus Lutzomyia. The occurrence of leishmaniasis in rodent species, the
geographic distribution of sand fly species in Nicaragua, and environmental factors
associated with the distribution of human cases of typical cutaneous leishmaniasis were
investigated. Three hundred ninety five rodents representing 17 species were collected
from 13 localities from August 2001–March 2006 and screened for Leishmania
infections. One Heteromys desmarestianus and one Peromyscus mexicanus were found
to be positive for leishmanial infections by PCR. This is the first report of Leishmania
infections in rodents in Nicaragua. Five hundred fifty six sand flies representing 12
species were collected from 8 localities, including Lutzomyia hartmanni, a new record
for this species in Nicaragua. The predominant sand fly species captured in western
Nicaragua were Lutzomyia longipalpis and Lutzomyia evansi. The predominant species
captured in central and eastern Nicaragua was Lutzomyia cruciata. The geographic distribution of sand flies in this study provides additional support to previouslypublished
reports of suspected vectors of Leishmania species that cause typical and
atypical forms of cutaneous leishmaniasis in Nicaragua.
Distribution data of human cases of typical cutaneous leishmaniasis obtained
from the Nicaraguan Ministry of Health, along with GIS and remotely sensed data of
elevation, precipitation, temperature, soil types and land use/cover classes, were used to
develop predictive logistic regression models for the presence or absence of human cases
within 151 municipalities. Mean annual precipitation and land use/cover were
determined to be the best environmental variable predictors for the occurrence of typical
cutaneous leishmaniasis.
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A Triple-Porosity Model for Fractured Horizontal WellsAlahmadi, Hasan Ali H. 2010 August 1900 (has links)
Fractured reservoirs have been traditionally idealized using dual-porosity models.
In these models, all matrix and fractures systems have identical properties. However, it
is not uncommon for naturally fractured reservoirs to have orthogonal fractures with
different properties. In addition, for hydraulically fractured reservoirs that have preexisting
natural fractures such as shale gas reservoirs, it is almost certain that these types
of fractures are present. Therefore, a triple-porosity (dual-fracture) model is developed in
this work for characterizing fractured reservoirs with different fractures properties.
The model consists of three contiguous porous media: the matrix, less permeable
micro-fractures and more permeable macro-fractures. Only the macro-fractures produce
to the well while they are fed by the micro-fractures only. Consequently, the matrix
feeds the micro-fractures only. Therefore, the flow is sequential from one medium to the
other.
Four sub-models are derived based on the interporosity flow assumption between
adjacent media, i.e., pseudosteady state or transient flow assumption. These are fully
transient flow model (Model 1), fully pseudosteady state flow model (Model 4) and two
mixed flow models (Model 2 and 3).
The solutions were mainly derived for linear flow which makes this model the
first triple-porosity model for linear reservoirs. In addition, the Laplace domain solutions
are also new and have not been presented in the literature before in this form.
Model 1 is used to analyze fractured shale gas horizontal wells. Non-linear
regression using least absolute value method is used to match field data, mainly gas rate.
Once a match is achieved, the well model is completely described. Consequently,
original gas in place (OGIP) can be estimated and well future performance can be
forecasted.
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Impacts of Natural Salt Pollution on Water Supply Capabilities of River/Reservoir SystemsLee, Chi Hun 2010 May 1900 (has links)
Salinity is a major determinant of where and how water resources are used
worldwide. Natural salt pollution severely constrains the beneficial use of large amounts
of water in Texas and neighboring states. High salinity loads in several major
river/reservoir systems, including the Brazos River, originate largely from salt seeps and
springs in isolated areas of the upper river basins located in the Permian Basin geologic
region.
Research objectives were (1) to improve salinity simulation capabilities of the
Water Rights Analysis Package (WRAP) modeling system, and (2) to develop a better
understanding of the occurrence, transport, and impacts of salinity in the Brazos River
and Lakes Possum Kingdom, Granbury, and Whitney. Water volume budgets and total
dissolved solids load budgets were developed for five river reaches covering 405 miles
of the upper Brazos River. Methodologies were developed for creating and applying
WRAP salinity input datasets. The WRAP modeling system was expanded and applied to the entire Brazos River Basin to investigate alternative modeling premises and
impacts of salinity and salinity control measures on water supply capabilities.
Water and salinity budget analyses of the Brazos River system based primarily
on measured stream flow, reservoir storage, and total dissolved solids data compiled by
the U.S. Geological Survey were performed to explore the characteristics of flow and
storage volumes and salinity loads and concentrations in the river/reservoir system.
WRAP salinity input datasets were developed based on results from the salinity budget
study. One dataset was designed and applied specifically for testing salinity routing
methods and calibrating salinity routing parameters. A second complete basin salinity
dataset was developed and applied to simulate the Brazos River Basin for alternative
management strategies. The results of the simulations demonstrate, for example, that
previously proposed salt control impoundments can significantly reduce salinity loads
and concentrations in the three reservoirs and at all locations on the Brazos River from
the impoundments downstream to the Gulf of Mexico.
The WRAP salinity simulation features are designed to provide flexibility in
combining water quantity simulation datasets from the Texas Water Availability
Modeling System or other sources, which may be very complex, with available salinity
data which varies in extent and format between different river basins. The modeling
capabilities demonstrated by the Brazos River Basin study can be applied in other river
basins as well.
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Evaluation and Effect of Fracturing Fluids on Fracture Conductivity in Tight Gas Reservoirs Using Dynamic Fracture Conductivity TestCorrea Castro, Juan 2011 May 1900 (has links)
Unconventional gas has become an important resource to help meet our future
energy demands. Although plentiful, it is difficult to produce this resource, when locked
in a massive sedimentary formation. Among all unconventional gas resources, tight gas
sands represent a big fraction and are often characterized by very low porosity and
permeability associated with their producing formations, resulting in extremely low
production rate. The low flow properties and the recovery factors of these sands make
necessary continuous efforts to reduce costs and improve efficiency in all aspects of
drilling, completion and production techniques. Many of the recent improvements have
been in well completions and hydraulic fracturing. Thus, the main goal of a hydraulic
fracture is to create a long, highly conductive fracture to facilitate the gas flow from the
reservoir to the wellbore to obtain commercial production rates. Fracture conductivity
depends on several factors, such as like the damage created by the gel during the
treatment and the gel clean-up after the treatment.
This research is focused on predicting more accurately the fracture conductivity,
the gel damage created in fractures, and the fracture cleanup after a hydraulic fracture treatment under certain pressure and temperature conditions. Parameters that alter
fracture conductivity, such as polymer concentration, breaker concentration and gas flow
rate, are also examined in this study. A series of experiments, using a procedure of
“dynamical fracture conductivity test”, were carried out. This procedure simulates the
proppant/frac fluid slurries flow into the fractures in a low-permeability rock, as it
occurs in the field, using different combinations of polymer and breaker concentrations
under reservoirs conditions.
The result of this study provides the basis to optimize the fracturing fluids and
the polymer loading at different reservoir conditions, which may result in a clean and
conductive fracture. Success in improving this process will help to decrease capital
expenditures and increase the production in unconventional tight gas reservoirs.
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Artificial Geothermal Energy Potential of Steam-flooded Heavy Oil ReservoirsLimpasurat, Akkharachai 2010 August 1900 (has links)
This study presents an investigation of the concept of harvesting geothermal energy that
remains in heavy oil reservoirs after abandonment when steamflooding is no longer
economics. Substantial heat that has accumulated within reservoir rock and its vicinity
can be extracted by circulating water relatively colder than reservoir temperature. We
use compositional reservoir simulation coupled with a semianalytical equation of the
wellbore heat loss approximation to estimate surface heat recovery. Additionally,
sensitivity analyses provide understanding of the effect of various parameters on heat
recovery in the artificial geothermal resources. Using the current state-of-art technology,
the cumulative electrical power generated from heat recovered is about 246 MWhr
accounting for 90percent downtime.
Characteristics of heat storage within the reservoir rock were identified. The factors with
the largest impact on the energy recovery during the water injection phase are the
duration of the steamflood (which dictates the amount of heat accumulated in the
reservoir) and the original reservoir energy in place. Outlet reservoir-fluid temperatures
are used to approximate heat loss along the wellbore and estimate surface fluid
temperature using the semianalytical approaches. For the injection well with insulation,
results indicate that differences in fluid temperature between surface and bottomhole are
negligible. However, for the conventional production well, heat loss is estimated around
13 percent resulting in the average surface temperature of 72 degrees C.
Producing heat can be used in two applications: direct uses and electricity generation.
For the electricity generation application that is used in the economic consideration, the net electrical power generated by this arrival fluid temperature is approximately 3 kW
per one producing pattern using Ener-G-Rotors.
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Technology and Economics Affecting Unconventional Reservoir DevelopmentFlores Campero, Cecilia P. 15 January 2010 (has links)
Worldwide, unconventional resources are important sources of oil and gas when
most conventional resources are declining and demand for hydrocarbons is growing. The
Masters? (1979) concept of the energy resource triangle suggest that the exploitation of
unconventional reservoirs is particularly sensitive to both technology and commodity
price parameters.
In the United States, production from unconventional reservoirs has been stimulated
by a combination of Federal tax credits, technical development programs -supported by
government agencies and private organizations- and high commodity prices. In this work,
the effect of technology and different economic events for selected unconventional oil
and gas plays in the United States was evaluated according to the concept of the Resource
Triangle Theory (RTT).
Studies conducted in the Austin Chalk -our textbook case- and other seven unconventional
plays in the United States have supported the RTT concept that high prices and
better technologies do result in more drilling activity and more oil and gas production
from unconventional reservoirs. For instance, two approaches were employed to support
RTT concept: Correlation study and Forecasting graphs. On the first one, correlations of commodity prices and technology with drilling activity
demonstrated that periods of high commodity prices coincide with increase in unconventional
producing wells approximately 75% from selected plays in this study.
The second one shows that high prices and technological advances also translate into
additional oil and gas production and reserves. This behavior was observed through the
analysis of a series of decline production curves using a VBA program in Excel that
compute oil and gas production volumes and their corresponding economic values under
specific conditions. The results indicated that maximum value of approximately $50 billion
oil plus gas would have been possible using conventional hydraulic fracturing technology
only. Moreover, subsequent episodes of high commodity allow the introduction
of new technologies that have boosted even more oil and gas production from the plays.
Great examples are the use of horizontal and multilateral wells which has opened up additional
areas for development, such as the Barnett Shale and the Bakken Shale. Using
horizontal wells has also revived older plays, such as the Austin Chalk. The combination
of horizontal well technology and water fracturing technology has led to a dramatic increase
in the development of both oil and gas from shale reservoirs. Current production
schemes suggest that the plays could produce an additional of $320 billion when producing
at rates higher than 5 BOE/day.
Our results confirm the concept of the resource triangle that natural gas and oil resources
can be produced from low quality resources when either product prices increase
or when better technology is available. The seven oil and gas plays studied in this research
are demonstrative examples.
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Flow unit prediction with limited permeability data using artificial neural network analysisThomas, Benjamin Hale. January 1900 (has links)
Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xxi, 280 p. : ill. (some col.), maps. Vita. Includes abstract. Includes bibliographical references (p. 150-152).
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