Nile Water Science & Engineering Journal

VOLUMES

Volume: Volume 8, 2015

Issue: Issue 2 , 2015, September

2-D Modeling of the Impact of Changing Hydraulic Parameters on the Flow Pattern at Rightangled Open Channel Confluences

On Wednesday, 1st of July, 2015. 11:16:44 AM
By Reda M radey

Topic: GIS and Remote Sensing applications in river engineering
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Abstract

In fluvial networks, confluences are inevitable and produce significant flow changes. Its presence is vital for the ecological connectivity, flood co read more

Estimation of the Climate Variability Impact on Water Resources in the Nyabugogo Swamp in Rwanda

On Wednesday, 1st of July, 2015. 11:16:44 AM
By Omar Munyaneza

Topic: Enviromental aspects of river engineering
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Abstract

Climate varies on all time scales, from one year to the next, as well as from one decade, century or millennium to the next. The complex nature of cl read more

Climate varies on all time scales, from one year to the next, as well as from one decade, century or millennium to the next. The complex nature of climate variability is a major obstacle to the reliable identification of global changes brought by the presence and activities of humanity on this planet. The aim of this study was to investigate the recent trends and variability of annual minimum, maximum and mean temperatures, evaporation, rainfall and streamflow trend in the Nyabugogo catchment (ca. 1,647 km2) with the goal of estimating the impact caused by this trend on water resources in the Nyabugogo swamp (220 ha). A data set of daily maximum, minimum temperature, rainfall and evaporation recorded at Kigali airport station from 1981-2013 were collected from Rwanda Meteorology Office, and the streamflow data (1981-2012) recorded at Cyamutara gauging station in Gasabo district were collected from Rwanda Natural Resources Authority (RNRA). Variations and trends of annual mean temperature time series, evaporation, rainfall and streamflow were examined. The Mann-Kendall test statistic was used to detect trend of climate variables and Pettitt tests was used to detect the abrupt change points. The Statistical Package for the Social Science (SPSS) was used to find out whether there is any correlation between them. Results show that annual mean temperature, evaporation and discharge revealed an increasing trend while rainfall trend is decreasing. The increasing temperature trends observed are possibly linked to human activities (e.g. deforestation, local urbanization). Pettitt tests revealed the abrupt change points in all climate parameters except discharge data whose analysis results are not significant due to a large number of missing data for a long period (around 50%). A strong correlation between temperature and evaporation was detected but the correlation between rainfall and discharge was found to be weak. This research provides possible major causes of such trends and correlations between climate variables and hence highlights their potential impact on water resources in the Nyabugogo swamp. less

Assessment of the Impact of Land Use Change on Nutrients Flow and Establishment of the Level of Key Pollutants of Nyangores River

On Wednesday, 1st of July, 2015. 11:16:44 AM
By francis karanja kigira

Topic: Enviromental aspects of river engineering
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This study was carried out with the aim of assessing the effect of Riparian land use/ land cover change on the hydrology and water quality of the uppe read more

Long-Term Morphological Changes along the 2nd Nile River Reach through Half Century after "HAD" Construction

On Wednesday, 1st of July, 2015. 11:16:44 AM
By Ahmed Fahmy

Topic: River morphology
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Citations: 1 | Reads: 89 | Downloaded: 10

Abstract

With the progress of High Aswan Dam "HAD" construction and filling the upstream reservoir, out of an average annual sediment load of 125 mi read more

With the progress of High Aswan Dam "HAD" construction and filling the upstream reservoir, out of an average annual sediment load of 125 million tons, only about 26.3 million tons passed downstream of the Old Aswan Dam "OAD" in year 1968 which was enormously decreased to about 2.0 million tons in year 2000. This led to conclude that, the average annual suspended sediment downstream "HAD" is enormously decreased from 1600 ppm before "HAD" construction to about 50 ppm. So far, several studies anticipated general degradation along the four Nile River reaches and sever local scour downstream the main hydraulic structures. Therefore, the present study aimed to explore the variation of water surface levels with time and location along the second river reach since the construction of "HAD" till year 2010. The daily records of flow discharges and the corresponding water surface levels along the second reach from year 1962 to 2010 were utilized to deduce the matching stage discharge rating curves. Following a similar study for the first Nile River reach, assessment of the attainable water surface levels for various periods and locations along the second river reach - at passing 200 million m3 / day – revealed that El- Mataana and El – Shanhoria gauge stations were the only sites subjected to water surface level decline and possible degradation after "HAD" construction. The decrease reached its maximum value of 0.225 m and 0.115 m at El-Mataana and El-Shanhoria gauge stations respectively at years 1979 and 1980 then turned over to increase and possible sedimentation at year 1992 for El-Shanhoria gauge station which reached 0.18 m and 0.355 m in years 2000 and 2010 respectively. On the other hand, the downstream part of the study reach from El-Sheikheya to Qena gauge stations did not subject to any decrease in water surface levels since "HAD" construction till year 2010. The monitored increase in water surface levels in year 2010 revealed a maximum value of 0.675, 0.355, 0.575 and 0.460 m at Luxor, El-Shanhoria, El-Sheikheya and Qena gauge stations respectively with respect to the condition before "HAD" construction. Moreover, the attained results for the condition before and after "HAD" construction revealed narrow distinction for the variation in longitudinal water surface slope which ranges between maximum and minimum values of 5.51 cm/km and 4.98 cm/km respectively. Therefore, unlike the concluded results for the first reach, the second one was not subjected to significant or considerable variations in the longitudinal water surface slope after "HAD" construction. Considering the increase in water surface level is due to general sedimentation of 0.516 m as an average value in year 2010, a total deposited material of 49.16 million m3 was worked out along the represented river reach. This led to conclude that the second River Nile reach is being subjected after "HAD" construction to general regular sedimentation and not degradation as expected from several studies. less

Assessment of Sediment Monitoring of Khashm el Girba Dam

On Wednesday, 1st of July, 2015. 11:16:44 AM
By Amira A. A. Mekawi

Topic: River morphology
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Khashm el Girba Dam (KED) on Atbara River was completed in 1964 with an initial storage capacity of 1.3 BCM. The main purpose of the dam is to supply read more

The Use of Statistical Performance Measures in Validation of MERIS Case 2: Water Quality Processors in Nasser Lake, Egypt

On Wednesday, 1st of July, 2015. 11:16:44 AM
By mohamed ahmed reda hamed

Topic: Other
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Citations: 1 | Reads: 111 | Downloaded: 5

Abstract

Nasser Lake is considered the main and strategic storage of fresh water in Egypt, so that, the preservation of the lake and continues monitoring of i read more

Morphodynamic Study of A River to Attenuate Flood Waves, Case Study of Nyabugogo River in Rwanda

On Wednesday, 1st of July, 2015. 11:16:44 AM
By L. Nzabonantuma

Topic: River morphology
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Downloaded: 3

Abstract

Floods are the most frequent and damaging of all type of natural disasters and annually affect the lives of millions people all over the globe. The s read more

Floods are the most frequent and damaging of all type of natural disasters and annually affect the lives of millions people all over the globe. The strategies (fight) against this natural disaster require knowledge mainly about river morphology, rainfall, land use, etc. The aim of this study is to assess different hydrological parameters that contribute to the Nyabugogo river flooding and evaluate whether geometric alteration would allow for a deduction in flood waves. Different approaches were used, firstly the analysis of hydrometeorological data collected nearby the Nyabugogo catchment in 2011 and ArcGIS approaches to delineate, calculate the area, slope of the catchment and the length of the river. Thereafter, statistical and hydrological analyses of the existing and acquired data were done by the use of Unit hydrograph method and computer program like MS Excel and ArcMap. The Exner principle was applied to analyze the law of mass conservation for sediment, also named “sediment balance”. Results showed that the total area of Nyabugogo catchment is 1,647 km2 while the length of the Nyabugogo River is 42.69 km. This length allows the river to drain most of runoff in the catchment. The calculated discharge of the surface runoff due to a 3 hours storm of 13 April 2007 was 33.04 m3/s. The knowledge of probability and frequency of high discharges and rainfall of Nyabugogo catchment that cause flooding helped to make strategies of flood management. Flooding occurred in Nyabugogo river and in its surrounding areas during rainy season are caused mainly by meanders at some Nyabugogo river reaches. These floods are not flash floods because they like to occur every year and for a long event. It is to say, response to flood hazards that can be undertaken in two ways; engineering approach, to control flooding such as elimination of meanders by a straight reaches of the river. In addition, regulatory approach like forestation of side hills where the agriculture is no longer practiced as well as creation of buffer zone along the Nyabugogo river channel, should be designed to decrease vulnerability to flooding. less

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