Volume:
Volume 4,
2011
Issue:
Issue 1 ,
2011,
July
Evaporation Modelling in Data Scarce Tropical Region of the Eastern Arc Mountain Catchments of Tanzania
On Sunday, 1st of May, 2011. 11:16:44 AM
By Birhanu Zemadim
Topic: GIS and Remote Sensing applications in river engineering
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Citations: 4 |
Reads: 456 |
Downloaded: 1
AbstractThis paper focuses on developing methods for both potential and actual evapotranspiration (ET)
models for the data scarce conditions of the Eastern A read more
This paper focuses on developing methods for both potential and actual evapotranspiration (ET)
models for the data scarce conditions of the Eastern Arc Mountains catchment of Tanzania. For reliable
estimation of the components of the hydrological cycle and plant water uptake, potential ET estimates
are required, and for catchment water balance actual ET estimates are needed. These potential and
actual ET estimates, however, depend on reliable and good quality data records. The study catchments
in this work are characterised by general lack of reliable meteorological (MET) data, though good
records of rainfall, flow and pan evaporation data do exist in a few places. In the study reported here
the Penman-Monteith (P-M) estimates were found to be closer to the pan evaporation model in areas
where reliable records of pan data exist. By comparison, estimates derived solely from temperature (i.e.
the Standard Thornthwaite method), were a lot lower. Assuming the P-M estimates to be reliable, new
temperature based regional equations were developed using data obtained from six climate stations.
The study also presents simpler methods for estimating actual ET from catchments. less
Regional Flow Duration Curve Estimation and its Application in Assessing Low Flow Characteristics for Ungauged Catchment. A Case Study of Rwegura Catchment-Burundi
On Sunday, 1st of May, 2011. 11:16:44 AM
By Joel Nobert
Topic: Hydropower Development
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Citations: 3 |
AbstractIn order to have a secure source of energy within the country, Burundi constructed Rwegura
hydropower plant on Kitenge River in September 1986. Recen read more
In order to have a secure source of energy within the country, Burundi constructed Rwegura
hydropower plant on Kitenge River in September 1986. Recently, the water level in the Rwegura
reservoir has decreased and this has resulted in a reduction in generated power and hence power
rationing. The reservoir is situated in an un-gauged catchment and therefore, there is a fundamental
need to develop a method that can be used to assess the hydrology in periods of low flow.
A flow duration curve for Rwegura ungauged catchment was developed through Regionalization
approach. Based on spatial rainfall pattern, a hydrological homogeneous region in which the catchment
belongs was derived. For each gauged site, a dimensionless monthly flow duration curve was derived
and a regional dimensionless flow curve was found by averaging the dimensionless flow duration
curves of all gauged sites. Multiple regression equation was then developed to find relationship
between mean monthly flow (index flow) for the gauged sites and catchment characteristics such as
catchment area, mean catchment slope, mean elevation of the catchment, station elevation, stream
length, stream slope and mean annual precipitation. The derived regression equation was used to find
the index flow at Rwegura ungauged site and thereafter the flow duration curve was found as a product
of dimensionless regional flow duration curve and index flow. The validation was based on the
comparison of the few available observed stream flow data (1980 – 1983) and the Nash efficiency
criterion was found to be 91%. The derived flow duration curve was used to characterize the low flow
in the range from 70% and 90% of time flow is equalled or exceeded. The monthly flow which is
equalled or exceeded 90% of time (Q90 )is 16.8m3 / s . This flow is known as the lowest flow
estimated for Rwegura and therefore it can be used to assess the reliability of hydropower generation in
Rwegura ungauged Catchment. less
Overlay Weighted Model and Fuzzy Logic to Determine the Best Locations for Artificial Recharge of Groundwater in a Semi-Arid Area in Egypt
On Sunday, 1st of May, 2011. 11:16:44 AM
By Peter Riad
Topic: GIS and Remote Sensing applications in river engineering
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Citations: 16 |
Reads: 234 |
Downloaded: 1
AbstractIn arid and semi-arid regions, where water scarcity is almost endemic, artificial recharge of
groundwater is one of the most effective techniques for read more
In arid and semi-arid regions, where water scarcity is almost endemic, artificial recharge of
groundwater is one of the most effective techniques for the augmentation of groundwater resources.
The overlay weighted models using ArcGIS is one the most common techniques for creating a
suitability map for the best locations of artificial recharge, however such models usually come up with
wide prioritized areas. In this study a new approach, Fuzzy logic, was applied too to give more accurate
suggestions by giving another classification inside each area of priority. Thematic layers were prepared
from some maps and satellite images by the remote sensing techniques for a semi arid area in the
western Nile delta in Egypt. These layers were classified, weighted and integrated in ArcGIS
environment and by the means of the overlay weighted model a suitability map which is classified into
number of priority zones was obtained. Numbers of points from different locations in each priority
zone in the suitability map were selected to be manipulated by fuzzy logic in Matlab. It was found that
fuzzy logic results give the same classification of the priority zones; moreover fuzzy logic could give
more priority classification for the selected points in each zone. less
Creating a Digital Elevation Model (DEM) from SPOT 4 Satellite Stereo-Pair Images for Wadi Watier - Sinai Peninsula, Egypt
On Sunday, 1st of May, 2011. 11:16:44 AM
By Moustafa EL-Sammany
Topic: GIS and Remote Sensing applications in river engineering
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Downloaded: 1
AbstractFlash Floods are one of the most damaging and costly natural hazards in Egypt, particularly in Sinai
Peninsula and the Eastern Desert. Therefore, hyd read more
Flash Floods are one of the most damaging and costly natural hazards in Egypt, particularly in Sinai
Peninsula and the Eastern Desert. Therefore, hydrological modelling and hydrodynamic simulations, to
understand and forecast flash flood events, are highly needed. Digital Elevation Model (DEM) is the
key component in such hydrological and hydrodynamic modeling, which can be used to derive a wealth
of information about the morphology and drainage network of a watershed. Unfortunately, limited
precise geographical and topographical information in the form of high resolution DEMs, in developing
countries, constrain such advanced hydrological and hydrodynamic modelling applications. This paper
describes the strategy of extracting high resolution and accurate DEMs from SPOT 4 stereo-pair
satellite images. The main objective of generating the DEM was for hydrological and hydrodynamic
simulation models for flash flood forecasting and as a significant component of an early warning
system. The research developed a methodology for generating 10 meter resolution DEM that was
calibrated against accurate land survey measurements. less
Integrated Flood and Drought Management for Sustainable Development in the Kagera River Basin
On Sunday, 1st of May, 2011. 11:16:44 AM
By Omar Munyaneza
Topic: Flood Management
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Citations: 10 |
Reads: 1045 |
Downloaded: 2
AbstractIntegrate Flood Management (IFM) integrates land and water resources development in a river basin,
within the context of Integrated Water Resources M read more
Integrate Flood Management (IFM) integrates land and water resources development in a river basin,
within the context of Integrated Water Resources Management (IWRM), with a view to maximizing
the efficient use of flood plains and minimizing loss to life. For flood management to be carried out
within the context of IWRM, Nile river basins should be considered as integrated systems. Socioeconomic
activities, land-use patterns, hydro-morphological processes, etc., need to be recognized as
constituent parts of these systems. The aim of this paper is to identify the flood and drought periods in
the river basin for future agricultural development and establish functioning integrated measures for
flood and drought management in the Kagera Basin, which is one of sub-basin of Nile basin. Digital
Elevation Model (DEM) map was used for Kagera river basin delimitation and its patterns (topography,
land use and land cover). Impacts of floods and drought on livelihoods of residents were outlined.
Survey methods were also used to derive a risk assessment methodology and management plans for
hazard prone communities. The flood disaster management strategic plan in the Kagera Basin contains
three phases such as prevention and mitigation before the occurrence, response in case of disaster, and
rehabilitation after the occurrence. Thus, the most important key strategy is the cooperation and coordination
across institutional boundaries, noting that the mandates of many institutions will either
cover only part of the river basin or extend well beyond the basin boundary. At the core of integration
is effective communication across institutional and disciplinary boundaries, which can take place only
if there is a perception of common interest. Emphasis was on the adoption of flexible strategies tailored
to each flood-prone region (characterized by their various physical, social, cultural and economic
aspects) – recognizing the importance of evaluating different options and their relative advantages and
disadvantages. less
Adaptation of Surface Water Modeling System for Sediment Transport Investigations in Lake Nasser
On Sunday, 1st of May, 2011. 11:16:44 AM
By Moustafa EL-Sammany
Topic: GIS and Remote Sensing applications in river engineering
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AbstractThe Nile River presents the main source of Egypt's water supply where it currently supplies most of the
total demands. Due to the great variabil read more
The Nile River presents the main source of Egypt's water supply where it currently supplies most of the
total demands. Due to the great variability between water supply and demands in quantity and timing, it
was decided to construct a century dam. In the period between 1964 and 1971, Egypt constructed the
Aswan High Dam. The construction of the dam entailed the development of an extensive reservoir,
known as Lake Nasser, which is considered the second largest man-made lake all over the world.
Optimum management of Lake Nasser requires a better understanding of the influence of the
hydrologic system of the lake. Hydrologic budgets that describe the sources and losses of water to lakes
are essential to many lake management decisions, for example, to adopt the best management practices
and to evaluate lake-restoration projects .However, many available hydrologic budgets lack the
necessary accuracy to define cause and effect clearly when lake levels begin to change .Sediment
transport and deposition is one of the main problem associated with large reservoirs. This paper
describes the process of generating the bathymetry of the lake bed surface and the development steps
for a 2-D hydrodynamic model for its flow fields and the application of the hydrodynamic model in the
sediment transport studies to explore the sedimentation problem at the lake entrance. The Surface
Water Modeling System (SMS), which contains RMA2 2-D hydrodynamic model, shows good
calibration and verification results .Hence, it can be utilized in the lake hydrodynamic analysis for
different scenarios. These results can be used as the input data into SED2D sediment transport model
for the sediment transport and deposition investigations in the lake. In addition, Geographic
Information System (GIS) tools, such as geo-spatial analysis tools, have been utilized in data
preparation, the analysis and estimation of the sediment deposition volumes and distributions. less
Effect of Change of Discharges at Dongola Station due to Sedimentation on the Water Losses from Nasser Lake
On Sunday, 1st of May, 2011. 11:16:44 AM
By mohamed mohamed abdel-latif mohamed
Topic: River morphology
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Citations: 7 |
Downloaded: 3
AbstractThe aim of this paper is to investigate the decrease of the water losses from Nasser Lake in recent years
than before. The water losses from Nasser L read more
The aim of this paper is to investigate the decrease of the water losses from Nasser Lake in recent years
than before. The water losses from Nasser Lake were estimated by the water balance method from
1964 to 2010. It is imperative to measure the Nile discharges at Dongola station accurately as these
discharges are used to estimate the water losses from Nasser Lake as an input to the water balance
equation. Investigations showed that sedimentation occurred at Dongola station and the cross sectional
area was reduced by 2.5-6%. Also, daily Flow measurements showed that the flow at Dongola was
reduced by 16-19%. This flow reduction is due to the formation of some islands in the location of the
station that divert part of the discharge at Dongola from the Main Nile to a newly formed channel that
discharges downstream the flow measuring station. The discharge of this new channel is not gauged
consequently it affects the computation of the water losses from Nasser Lake. It is very crucial to find
another location at the Main Nile to measure the discharges that flow to Nasser Lake instead of
Dongola to alleviate this problem. less
Prediction of Breach Formation Through the Aswan High Dam and Subsequent Flooding Downstream
On Sunday, 1st of May, 2011. 11:16:44 AM
By SAMIR IBRAHIM
Topic: Other
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Citations: 7 |
Reads: 2259 |
Downloaded: 2
AbstractAll over the world, there are many dams failure due to many different reasons. These reasons range
from structural instability to some hydraulic cond read more
All over the world, there are many dams failure due to many different reasons. These reasons range
from structural instability to some hydraulic conditions. The dam failure may occur due to overtopping,
seepage or piping through the dam body or its foundation. There are some situations which may cause
sudden failure to the dam like earthquakes, landslide or even possibility of terrorist attacks. Failure of
dams can result in loss of life, property and environmental damage, and have economic repercussions.
The Aswan High Dam, (AHD) plays an important role in the main system of Egyptian irrigation
system, hydropower, flood control, drinking water. This importance is related to that, the population
majority of Egypt is located downstream the dam site accompanied with the high portion of the
national economic activities as agriculture and industries.
The present paper assesses the risk of the Aswan High Dam breaching due to overtopping, numerically.
All related data were collected and analysed. A suitable numerical dam breach model was chosen and
selected to be implemented. Three scenarios were designed to represent minimum, normal and
maximum flood flow to the lake at normal water level, respectively. Other three scenarios represent the
same flood configuration flow to the lake at maximum water level conditions, respectively. The six
scenarios were simulated using the dam breach model. The expected impacts of the Aswan High Dam
failure, due to overtopping, were analysed.
Outflow hydrographs due to the failure were obtained. The Nile River downstream Aswan High Dam
until Delta Barrage was simulated using 1D 2D model. The obtained results from dam failure of the
scenario of maximum inflow to normal Nasser Lake water level were applied to 1D2D model. A risk
assessment to the dam breaching was achieved. Results of the calculated show the flood wave
propagation in terms of inundations maps, flows, water levels, flood arrival time, and flow velocities
along the water course from Aswan High Dam to delta Barrage. The results of this investigation could
be further applied and could assist decision makers to set a plan to confront the risks of the Aswan
High Dam failure. less
Generation of Rainfall Intensity Duration Frequency Curves For Ungauged Sites
On Sunday, 1st of May, 2011. 11:16:44 AM
By Eman El Sayed
Topic: Other
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Citations: 32 |
Reads: 167 |
Downloaded: 4
AbstractThe rainfall intensity-duration-frequency (IDF) relationship is commonly required for planning and
designing of various water resource projects. Many read more
The rainfall intensity-duration-frequency (IDF) relationship is commonly required for planning and
designing of various water resource projects. Many sets of relationships have been developed and used
in several parts of the world. The IDF relationship is a mathematical relationship between the rainfall
intensity, the duration and the return period. This relationship is determined through statistical analysis
of samples of records at proper meteorological stations. Sinai Peninsula in the North East part of Egypt
has a network of daily rainfall recording rain gauges since 1988. A total of six different durations
ranging from 5 minutes to 24 hours for return periods of 2, 5, 10, 25, 50, 100 and 200 years were
analyzed. The IDF curves and isopluvial maps for the region are developed using the available rainfall
data. The main aim of this paper is to construct IDF curves for the region using rainfall frequency
analysis techniques. Also, the paper proposes regional IDF formula to estimate rainfall intensity for
various return periods and rainfall durations at ungauged sites. less
Evaluation of the Flow Characteristics in the Intake Structure and Pump Sumps Using Physical Model
On Sunday, 1st of May, 2011. 11:16:44 AM
By SAMIR IBRAHIM
Topic: Hydraulic Structures
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AbstractA physical model was built at an undistorted scale of 1:8.724 tested the original design of the
circulating cooling water flows to onshore intake str read more
A physical model was built at an undistorted scale of 1:8.724 tested the original design of the
circulating cooling water flows to onshore intake structure and to test the flows to an inland pump
house intake through four pipes. The capacity of origin water intake including circular and service
pumps is 52.178 m3/s. The model was built and operated in accordance with Froude-number similitude.
The aim of the model study is to test the design of the pump intake and to investigate any modifications
on the design which may be needed to enhance the efficiency of the pump intake structure. Also some
sensitivity tests were done at several water levels of the pump house. The model was operated at high,
minimum water conditions and at different operation modes. Physical model is expected to help in
evaluating the operation, to aid in design or modifying of the intake structure and to test any
recommended modifications, if needed.
The results of the model test is used to determine if the initial design of the pump sump structure would
be susceptible to surface and sub-surface vortices, pre-swirl entering pumps and excessive fluctuation
in the velocities at the pump bell throat according to Hydraulic Institute(HI) specifications
The results of the tests showed that the rotations of the roto-meters are within the allowable limits
specified by the HI criteria in all operation modes. No vortices more than type 2 was observed near the
bell mouths of the circular and service water pumps at minimum water level conditions. In the high
water level conditions, it was observed that vortices of type 3 or 4 appeared upstream of the curtain
wall and move downstream near the bell mouth of circular water pumps. Those vortices disappeared
after modifying the top of the baffle wall from elevation of minimum water to high water level. It was
found that vortex type 6 was appeared when submergence above suction bell inside the pump house
was about 1.5 times the pump column diameter, 2.2 of the pump impeller throat diameter and 1.05 of
the suction bell diameter. Continuous type 5 or 6 surface vortices were observed upstream of all four
intake pipe inlets for minimum water level cases and the vortices disappeared by closing the flow
entrance between the intake pipe inlet cap slab and the stop logs slots. The velocity measurements
taken inside the pump suction pipes showed that the flow velocity at the impeller location is uniform in
magnitude, within ± 10 % of the mean velocity. less