Volume:
Volume 5,
2012
Issue:
Issue 2 ,
2012,
September
Water Distribution Changes In Tuweir Minor Canal, Gezira Scheme, Sudan
On Sunday, 1st of July, 2012. 11:16:44 AM
By Ertiban Wondifraw Woldegebriel
Topic: River morphology
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AbstractGezira Scheme (GS) was designed for cotton production. It was designed to serve water to 50% of its
gross command area in two consecutive growing sea read more
Gezira Scheme (GS) was designed for cotton production. It was designed to serve water to 50% of its
gross command area in two consecutive growing seasons (summer and winter). But later, in the 1960s,
a crop diversification and intensification policy was implemented in the Scheme. That results to operate
the system over its capacity; together with an increment of the actual sedimentation rate from the Blue
Nile’s catchment, silt to enter the canal system has increased. Consequently, operation and
maintenance (O&M) costs have risen to a point that is beyond the capacity of the government. This in
turn could affect water distribution. However, it was not clear, where and how the water distribution
change in the scheme. This paper investigates the water distribution on a minor canal called Tuweir
which is a part of a big project, the Blue Nile programme, implemented to analyse the situations on
operation and maintenance (O&M) in depth. Both socio-economic and bio-physical data were collected
through interviewing, field observations, and measurements. Through a wide range of scientific
literature and (local) policy documents the research could be designed and field data could be crosschecked.
The result implies, though it is difficult to claim that water distribution in the past was well
planned and optimal, there was at least relatively formal, predictable and specified water indenting
system that roughly corresponding with estimated crop water requirements and the canal capacity.
However, currently no scientific approach of crop water calculation takes place nor does the canal
capacity feature in the balance at all.
Factors like the operation of the FOPs (Field Outlet Pipes) by farmers themselves as well as, their
irrigation perceptions negatively affect the water supply security. The interplay of these factors has
created unequal, unreliable and unscheduled water distribution between tertiary units (numbers) of the
Tuweir minor canal. The impacts of the water distribution changes produce both long term (out
migration of farmers, cropping pattern changes and deterioration of the system); and short term effects
(yield reduction, conflict between farmers, additional costs for water pumping...) on the water users. less
Developing an Optimum Multipurpose Reservoir Operation Policy under Uncertain Conditions
On Sunday, 1st of July, 2012. 11:16:44 AM
By Mohammed Abdallah
Topic: Other
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Citations: 3 |
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AbstractThe aim of this paper is to develop a flexible operation policy for a multipurpose reservoir under
uncertain conditions and incomplete information in read more
The aim of this paper is to develop a flexible operation policy for a multipurpose reservoir under
uncertain conditions and incomplete information in arid and semi-arid regions where managing uneven
water quantity distribution is a challenging task. A set of statistical parameters and fuzzy rule based
models have been applied taking into account different parameters uncertainty of future inflow
scenarios, storage capacity deterioration due to sedimentation, and demands variability for Roseires
reservoir at Blue Nile-Sudan- . A Fuzzy Rule Based (FRB) membership functions have been designed
depending on statistical parameters of time series analysis accompanied with different future climate
change perspectives for inflow scenarios at the Eastern Nile region, while a statistical analysis and
expert opinions have been used to shape the different storage, releases, and demands membership
functions in order to obtain the optimum release. The developed policy satisfactorily handles the
conflict between different design purposes namely, irrigation, hydropower, and domestic supply during
low flow season while presenting a good compromise between flood protection, filling, emptying and
sediment flushing processes during flood season. On the other hand the adopted approach shows a
potential competency of considering the different future scenarios uncertainties in addition to good
flexibility in terms of modification, adaptation, simplicity of learning and applying by the reservoir
operators at the field when user friendly GUI model windows is used, which consider a step towards
filling the gap between scientific research’s results and field practice. less
Assessment of groundwater potentiality of northwest Butana Area, Central Sudan
On Sunday, 1st of July, 2012. 11:16:44 AM
By Khalid Elsayed Zeinelabdein
Topic: GIS and Remote Sensing applications in river engineering
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Citations: 4 |
Reads: 485 |
Downloaded: 2
AbstractButana plain is located 150 Km east of Khartoum, it is the most important area for livestock breeding
in Sudan. Nevertheless, the area suffers from a read more
Butana plain is located 150 Km east of Khartoum, it is the most important area for livestock breeding
in Sudan. Nevertheless, the area suffers from acute shortage in water supply, especially in dry seasons
due to climatic degradation. Considerable efforts were made to solve this problem, but little success
was attained. Hills, hillocks, ridges and low lands are the most conspicuous topographic features in the
studied area. Geologically, it is covered by Cenozoic sediments and sandstone of Cretaceous age
unconformably overlying the Precambrian basement rocks. The objective of the present study is to
assess the availability of groundwater resources using remote sensing, geophysical survey and well
inventory methods. Different digital image processing techniques were applied to enhance the
geological and structural details of the study area, using Landsat (ETM +7) images. Geo-electrical
survey was conducted using Vertical Electrical Sounding (VES) technique with Schlumberger array.
Resistivity measurements were conducted along profiles perpendicular to the main fracture systems in
the area. The present study confirms the existence of two groundwater aquifers. An upper aquifer
composed mainly of alluvial sediments and shallow sandstone is found at depths ranging between 20-
30 m, while the lower aquifer is predominantly Cretaceous sandstone found at depths below 50 m. The
seasonal streams represent the main source of groundwater recharge in the study area. Groundwater
movement within the Cretaceous Sandstone aquifer shows different flow directions, among which the
south and northeast are the dominant. The aquifers are characterized by average hydraulic conductivity
of 8.0x10-3 m/min and the transmissivity (T) of 3.85x10-2 m²/min. Groundwater samples obtained from
each of the aquifers are totally different in terms of hydrochemical properties. The groundwater in the
upper aquifer is characterized by TDS of 150-1800 ppm. This water is mainly dominated by alkaline
earth with calcium and magnesium increasing with the flow direction. The groundwater in the
sandstone aquifer is predominantly of the chloride- calcium type that reflects deficiency of recharge. less
Surface Water Resources Assessment in the Rwasave Marshland, southern Rwanda
On Sunday, 1st of July, 2012. 11:16:44 AM
By Omar Munyaneza
Topic: Other
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AbstractWith a growing world population and the need of food security, surface water resources can play a
great role worldwide. The water resources of the Rw read more
With a growing world population and the need of food security, surface water resources can play a
great role worldwide. The water resources of the Rwasave catchment support a diverse range of
activities including irrigated horticulture, broad scale cereal cropping, grazing and forestry. The aim of
this study is to analyze the average annual rainfall and runoff of Rwasave marshland and computes a
water balance of this marshland to improve food production. Rwasave marshland (91.2 km2) is the
largest sub-catchment of Migina catchment located in southern Rwanda in the Kagera river basin,
upstream of Nile river basin. A DEM map with 90 m resolution that was prepared from a satellite
image of 1999 has been used for catchment delineation. After hydrological processing operations using
ILWIS software program, a digitization of the catchment area of marshland has been conducted. The
hydrological analysis of the data from different meteorological stations was performed using statistical
analysis and a water budget method. The results of water balance produced for this research show the
total annual inflows of 162.9 millions of cubic meters, total annual outflows as 98.5 millions of cubic
meters and a change in water storage within the marshland is about 64.4 millions of cubic meters all
around one hydrological year. This study brought some improvement on crops production in this
marshland by proving the water balance of Rwasave marshland to Agricultural Engineers. Farmers
who are using this marshland will benefit from these results. The improved technologies of water
saving and land conservation are sufficient to reach a good harvest, if peoples are informed about
hydrological conditions. less
Prediction of the Chemical Oxygen Demand (COD) Using Artificial Neural Networks in the Rosetta Nile River Branch of Egypt
On Sunday, 1st of July, 2012. 11:16:44 AM
By Mona Soliman
Topic: Other
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AbstractOwing to discharge of primary, secondary and un-treated wastewater to surface water, associated with
increases in population, urbanization and indust read more
Owing to discharge of primary, secondary and un-treated wastewater to surface water, associated with
increases in population, urbanization and industrialization, the water quality of the Nile has been badly
affected. Thus, there is an urgent need for new tools to improve process knowledge to support pollution
control. One such tool is the Artificial Neural Network (ANN) modelling, which can be effective for
understanding and predicting non-linear relationships. This paper discusses the development of an
Artificial Neural Networks (ANNs) model for the prediction of the Chemical Oxygen Demand (COD)
in the Rosetta Branch, in the north-west of the Nile Delta, EGYPT. After many runs, by the model,
with different water quality parameters and verifying the model outputs with the actual values
measured in the laboratory, the following variables were decided to be the input data to the model:
biological oxygen demand (BOD), dissolved oxygen (DO) and water temperature for the prediction of
chemical oxygen demand in the Rosetta branch. Four hidden-layers were developed, with four neurons
for each layer, using the hyperbolic function. The study showed that the error percentage, between the
actual and predicted records, ranged from close to 0 to 14 %. However, it is demonstrated that the
artificial neural network (ANN) is capable of modeling the chemical oxygen demand concentration
with good accuracy when proper variables are used. less
Effect of Flow Deflector above End Sill on Minimizing Negative Velocities Downstream Stilling Basin
On Sunday, 1st of July, 2012. 11:16:44 AM
By Neveen Yousif
Topic: Other
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Downloaded: 1
AbstractThe main aim of this research is to investigate experimentally the effect of the presence of cylindrical
deflectors over end sill (with different rad read more
The main aim of this research is to investigate experimentally the effect of the presence of cylindrical
deflectors over end sill (with different radii and locations) on minimizing or eliminating the near bed
negative velocity downstream the stilling basin, in order to reduce the dangerous effect of it on the bed
and the floor.
Three different parameters of the deflector were investigated to determine the criteria that would
produce the best performance. These parameters are the size, vertical position above the end sill and
lateral location. The best ratio between the deflector diameter and its position above the end sill that
gives the best performance of the deflector (minimum –ve velocity) was determined. Also, the best
lateral location was determined by using one of the deflectors with its best vertical position.
The cylindrical deflector proved to be an effective tool for eliminating the near bed negative velocity
D.S the stilling basin as the negative velocity was reduced by about 85-100% using this effective tool.
Also, the effect of deflector size and position on the characteristics of hydraulic jump formed U.S the
end sill was investigated. less
Comparative Performance of Soil Moisture Accounting Approach in Continuous Hydrologic Simulation of the Blue Nile
On Sunday, 1st of July, 2012. 11:16:44 AM
By K.E. Bashar
Topic: Enviromental aspects of river engineering
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Citations: 9 |
Downloaded: 1
AbstractContinuous hydrologic models account for the soil moisture balance in the catchment over a long-term
period. Different hydrologic physical processes read more
Continuous hydrologic models account for the soil moisture balance in the catchment over a long-term
period. Different hydrologic physical processes such as: interception, surface depression storage,
infiltration, soil storage, percolation, and groundwater storage are considered in continuous hydrologic
modeling. In this paper, the Hydrologic Modeling System (HMS) and the SMAR model were used for
continuous hydrologic simulation of the Blue Nile. Both the models encompass Soil Moisture
Accounting (SMA) algorithm to simulate the long-term relationship between rainfall, runoff, storage,
evapotranspiration, and soil losses in the Blue Nile but only differ in level of complexity. The objective
of this paper is to evaluate the performance and potentiality of the SMA algorithm using the two
models with application on the Blue Nile as a case study in the Nile basin.
The models performance was tested using five criteria namely, the Coefficient of efficiency (R2) to
measure the relative improvement of the models performance over a naïve model, whose forecast for
all times is the mean of the flows in calibration, the Coefficient of determination (r2) to describe the
proportion of the total variance in the observed data that explained by the model, the Index of
agreement (IoA) to overcome the insensitivity of the correlation-based measures to differences in the
observed and the model-simulated means and variances, the index of volumetric fit (IVF) for
volumetric match of the observed flows with the estimated flow indicating water balance, and the
Relative error (RE) of the peak to reproduce the observed peak.
Daily areal rainfall for seven years (1990-1996) was obtained by arithmetic mean of ten rain gauging
stations. Daily evaporation and runoff for the same period were obtained and used. 1k hydro-dem
Digital Elevation Model (DEM) of the Blue Nile was used to delineate the catchment and obtain its
area. The data was split into 5 years for calibration and 2 years for verification. The models are applied
as lumped systems.
Despite the lumping of the input, the output and the parameters accounting for the physical processes in
the catchment, the two models showed satisfactory performance. The SMAR accounted for more than
90% of the initial variance and consistently performed better than HMS based on four performance
indices. The HMS model showed better performance in reproducing the overall peak.
It was found that under the lumped modelling case and forecasting purpose, the level of complexity of
the model and its parameters does not garantee any improved performance. This is clear from the fact
that simple models like SMAR performs better than models like HMS. less
Optimizing sediment sampling programme in a catchment. The case of Pangani River Basin
On Sunday, 1st of July, 2012. 11:16:44 AM
By Preksedis Marco Ndomba
Topic: Enviromental aspects of river engineering
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Citations: 26 |
Downloaded: 1
AbstractIn previous sedimentation studies in Pangani River Basin located in the Northeastern part of Tanzania,
it has been assumed that data set available fo read more
In previous sedimentation studies in Pangani River Basin located in the Northeastern part of Tanzania,
it has been assumed that data set available for rating curve construction or estimating sediment
yield/load represents a near-optimum data collection scheme and that estimates of the errors involved
are minimum estimates. Other researchers elsewhere have done little as well, in quantifying errors due
to varying number of data points. Besides, the performance of the sediment sampling programmes have
been compromised due to lack of information on informed hydro-climatic variables triggering much
upland soil loss and delivery of sediment loads to catchment outlets. Therefore, this study
quantitatively estimated the number of data points required for optimal sediment sampling through
developing an “efficient” rating curve with informed hydro-climatic condition. This was achieved by
optimization techniques using readily available 291 sub-daily data points on sediment concentration
and stream flows. A total of 274 randomly generated samples of different sizes were used to fit the
rating curves by Ordinary Least Square (OLS) approach. However, the analysis was constrained to
using more than 16 data points as minimum number for a two-parameter model such as rating curve
parameterization/regression. The developed rating curves were used to estimate the annual sediment
loads during the sediment sampling programme period. The Relative error in percent (RE) as index of
performance between estimated load and “actual load” was computed. RE less than 20% was
considered as satisfactory for engineering practices. Findings showed that a sediment concentration
sample of less than 30 data points; i.e., 17, 26, and 27; covering critical hydrological conditions is
adequate. An independent analysis indicates that these samples are from selected runoff events in
months of March, April, May, and June. Events of April mostly dominated the sediment delivery to the
catchment outlet. As this result is based on one year sediment sampling programme, thus there is a
need to validate the results using recent sediment flow data in the same catchment. The sampling
programme proposed is site specific, so it may not be extended easily to other catchments. Further
studies should also analyze the reliability of the proposed sample size for optimal sampling programme
in Pangani River Basin and other catchments. less
Dynamics of land use and land cover changes and implications on river flows in Simiyu River catchment, Lake Victoria Basin in Tanzania
On Sunday, 1st of July, 2012. 11:16:44 AM
By Deogratias M.M. Mulungu
Topic: Enviromental aspects of river engineering
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Downloaded: 1
AbstractThe Simiyu River catchment in the Lake Victoria Basin is important for agriculture, fishing and
livestock keeping. However, increased pressure on the read more
The Simiyu River catchment in the Lake Victoria Basin is important for agriculture, fishing and
livestock keeping. However, increased pressure on the land due to rise in population, expansion in
agriculture to include the wetland areas, are threatening the sustainability of the catchment resources.
Anecdotal evidence has it that the catchment has tremendously changed and the changes have impacted
on the water resources of the catchment. Nevertheless, very little is known about the quantities of the
changes and the implications of the changes on river flows. Therefore, a study was conducted to
quantify the land-use and land-cover changes for the 1980s and 2000s and subsequently investigated
the implications of the detected changes on flow regimes of the Simiyu River. Remote sensing and GIS
techniques were used to inventory temporal changes of land use and land cover changes in the
watershed. The ground truth data were collected using a GPS and used in verification of the land
covers. The post-classification comparison method was used to assess land use and cover changes
followed by the estimation for the rate of change. Hydrological data were analyzed to reveal the
alterations and trends for two time periods; pre-1988 and post-1988. The study revealed the
transformation of larger area of the catchment to agriculture with an annual increase of 29.41%,
followed by forest (+4.69%) and settlement (+4.68%). The wetland area was found to decline at a rate
of -3.33% annually and the grassland at -4.06%. The river flows were found to be variable within and
between the years, and sensitive to land use and land cover changes. There was a slight shift of the
timings for peak flows in the recent period than the former and declining magnitudes of mean and base
flows. The study concludes that the modification of the land use and cover has resulted in changes in
temporal distribution of catchment runoff. The study highlights the importance of remote sensing in
understanding the land use and land cover dynamics and the implications of changes on catchment
runoff for informed decisions on the sustainability of the catchment resources. less
