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УДК 528.082
ИССЛЕДОВАНИЕ МНОГОЦЕЛЕВОГО НАЗНАЧЕНИЯ ДАМБЫ КАИНДЖИ С ПОМОЩЬЮ БАТИМЕТРИЧЕСКОГО И ОБЪЕМНОГО МЕТОДОВ СЪЕМКИ
Рафаел Эхигиатор Иругхе
Университет Бенина, PMB 1154, Нигерия, штат Эдо, доктор наук, доцент геодезии и геома-тики, кафедра геоматики, факультет экологии, тел. (234)803-368-10-19, е-mail: raphael. ehigi ator@uniben.edu
Оладозу С. Олушола
Университет Бенина, PMB 1154, Нигерия, штат Эдо, преподаватель II категории, кафедра геоматики, факультет экологии, тел. (234)806-521-18-10, е-mail: olushola.oladosu@uniben.edu
При надлежащем анализе данных батиметрии можно получить точное представление
0 топографии глубин и объеме воды в дамбе в определенный период времени. Была выполнена батиметрическая съемка дамбы Каинджи с помощью эхолота MIDAS и двухчастотной GPS Trimble. Анализ производился с использованием Surfer 10. Подсчитанный объем воды составил 1 322 676.662 955 мм3. Общий объем, потребляемый турбинами в день, 1 896 000 л, в то время как потребление воды на душу населения в день - 5 518 445 л и 24 964 500 л соответственно минимальное и максимальное. Объем, оставшийся после потребления воды, составил 98 % от подсчитанного объема.
Ключевые слова: дамба Каинджи, батиметрия, объем, многоцелевой эффект, замер глубины, эхолот, турбины, потребление воды на душу населения.
PROSPECTING INTO THE MULTIPURPOSE BENEFITS OF KAINJI DAM USING BATHYMETRIC AND VOLUMETRIC SURVEY TECHNIQUES
Raphael Ehigiator Irughe
University of Benin, PMB 1154, Nigeria, Edo State, D. Sc., Associate Professor of Geodesy and Geomatics Engineering at the Department of Geomatics, Faculty of Environmental Sciences, tel. (234)803-368-10-19, e-mail: raphael.ehigiator@uniben.edu
Oladosu S. Olushola
University of Benin, PMB 1154, Nigeria, Edo State, Lecturer II at the Department of Geomatics, Faculty of Environmental Sciences, tel. (234)806-521-18-10, e-mail: olushola.oladosu@uniben.edu
Data from bathymetry when properly analyzed provide a good understanding of depth topography and the volume of water present in a dam at a particular period of time. Bathymetry survey of Kainji Dam was carried out using MIDAS Echo Sounder and Trimble Dual Frequency GPS. Data analysis was done using Surfer 10. The result of computed volume gave
1 322 676.662 955 Mm3. The total volume consumed by the turbines per day gave 1 896 000 L while that of per capita water use per day per inhabitant gave 5 518 445 L and 24 964 500 L at minimum and maximum rates respectively. Volume left after all withdrawers was 98 % of the computed volume.
Key words: Kainji Dam, Bathymetry, Volume, Multipurpose benefits, Sounding, DGPS, Echo Sounder, Turbines, Per Capita Water Use.
Introduction. In ancient times, dams were built for the single purpose of water supply or irrigation. As civilizations developed, there was a greater need for water supply, irrigation, flood control, navigation, water quality, sediment control and energy. Therefore, dams are constructed for a specific purpose such as water supply, flood control, irrigation, navigation, sedimentation control, and hydropower. A dam is the cornerstone in the development and management of water resource development of a river basin. The multipurpose dam is a very important project for developing countries, because the population receives domestic and economic benefits from a single investment [1]. Multipurpose dams are built for multipurpose use.
Bathymetry. NOAA, [2], defined bathymetry as the study of the "beds" or "floors" of water bodies, including the ocean, rivers, streams, and lakes. The term "bathymetry" originally referred to the ocean's depth relative to sea level, although it has come to mean "submarine topography," or the depths and shapes of underwater terrain. Bathymetry is the foundation of the science of hydrography, which measures the physical features of a water body. Hydrography includes not only bathymetry, but also the shape and features of the shoreline; the characteristics of tides, currents, and waves; and the physical and chemical properties of the water itself.
Study Area. The study area is as shown in figure 1, the left hand side is the topographic map merged with google earth satellite imagery for clearer view. The coordinates of Kainji dam is given as; 09°51'45" N and 04°36'48" E. It is a dam across the Niger River in Niger State of Northern Nigeria [4].
Fig. 1. Topographical Map and google earth imageries of the study area.
Source (google earth) and [3]
Methods. The bathy Survey boat used was an open fiber boat of 2 metre width, 5 metre length and 0.5 metre draft, mounted with 2 x 85 HP engines. The bathymetric survey equipment was mounted on an aluminum vessel with the transducer and GPS unit located over the side, the hydrographic system included a GPS receiver with a built-in radio, a depth sounder, a helmsman display for navigation, a computer, and hydrographic system software for collecting the underwater data. On-board batteries
powered all the equipment. The shore equipment included a second GPS receiver with an external radio. The shore GPS receiver and antenna were mounted on survey tripods over a known datum point and powered by a 12-volt battery [5].
Fig. 2. Survey Boat, MIDAS Surveyor Echo Sounder, Toshiba Laptop and Hypack Navigation System software window. Source [5]
Area Computation. The area of expanse of land covered by the dam through traverse was computed using cross coordinate method in the determinant form as:
Where: N1 .... Nn, are Northings and E1 .... En, are Eastings
The product of the coordinates along full lines is taken positive and along dashed line is taken negative, therefore the area is given as:
Area (m2) = 1 (N1E2 - EtN2 + E2N3 - E2N3...........+NnEt - EnNt) (i)
Volume Computation. The computation of volume of water in the dam's reservoir was done using the trapezoidal and Simpson's rules which can also be verified with the help of surfer 10 software. Equation (i) is the trapezoidal rule while equation (ii) is the Simpson's rule.
Volume (m3) = ^(A1 + An + 2(A2 + A3 + ••• + An-1) (ii)
Volume (m3) =j [A0 + 4A1 + 2A2 + 4A3 ... + 2An-2 + 4An-1 + An] (iii)
Where, V = volume, A1 = area of first section, An = area of last section, D = the common distance.
Fig. 3. 3D Bottom topography of the reservoir produced in surfer 10
The volume of water computed from the data obtained from the reservoir gives the following values with different rules as follows: Trapezoidal Rule: 1 320 045.659 589 Mm3
Simpson's Rule: 1 322 676.662 955 Mm3
Simpson's 3/8 Rule: 1 320 951.922 289 2 Mm3
Figure 3b, depict the 3D depth topography of Kainji dam and elevation points in gray scale.
Results and Discussions. The results presented in figure 3 and 4 are the 3D bottom topography and the contour maps of the kainji reservoir bed.
Figure 4, shows, the contour representation of the reservoir and the gray scale variations.
Volume of water needed to run the turbines. The amount of head available in hydro energy system determines the amount of power available from the water as Power is proportional to Head x Flow. The flow of water through the turbine is normally expressed in litres per second, (liter/s) or cubic metres per second (m3/s) and refers to the quantity or volume of water used by the turbine to turn the shaft [5]. [5], also noted that 3m3/s which is equal to 3,000L/s of flow is needed to produce 1MW of power and when multiplied by the total power output given in megawatts gives the amount of water required to produce power per second. The Kainji dam has eight plants with total installed capacity of 760 MW (four-80 MW, two-100 MW and two-120 MW) [7]. Volume of water needed for 4 turbines per day = 3000 x 80 x 4 = 96000 liters Volume of water needed for 4 turbines per day = 3000 x 100 x 2 = 600000 liters Volume of water needed for 6 turbines per day = 3000 x 200 x 2 = 1200000
liters
Total volume of water needed to run the 8 turbines per day = 1896000 liters
Fig. 4. Contour representation of the reservoir produced in surfer 10
Per capita water use. According to [8], per capita water use is calculated by dividing the total amount of water withdrawn from all water suppliers by the population. The per capita proposed water usage by the Kainji (settlement) inhabitants with estimated population of 44,500 is displayed in the following figures. Figures 5 and 6 show the percentage of the proposed water consumption per inhabitant per day. The volume of water use per person per day gives 124.0 Liter/person/day for minimum and 561.0 Liter/person/day for maximum. Total water consume by the entire population per day is equal to 5 518 445 Liter/day at minimum rate and 24 964 500 Liters/day at maximum rate.
1%
QBrushing teeth QCooking a meal Flushing toilet □Washing hands
Dish washer □Washing machine □Shower □Cleaning car
Fig. 5. Percentage of water use per person per day (Minimum)
QBrushing teeth □Cooking a meal Flushing toilet □Washing hands
Dish washer QWashing machine □Shower □Cleaning car
Fig. 6. Percentage of water use per person per day (Maximum)
Fig. 7. Total volume consumed by turbines and per capita use per day (liters)
Figure 7, shows the total consumption capacity, which is the sum of the total consumption by the turbines per day and per capita use per day. It is clear that 77 % goes to the turbines while 23 % sum up for per capita use.
0%
0%
2%
Computed Volume (L)
Total vol. consume by turbines
Minimum Per capita use
Maximum per capita use
Fig. 8. Total volume consumed by turbines and per capita use per day less
computed volume (liters)
Figure 8, shows the total consumption capacity, which is the sum of the total consumption by the turbines per day and per capita use per day minus the computed volume. It can be observed that 98 % is the remaining volume after taken away the total withdrawers which is just 2.0 %.
Acknowledgement. The authors are grateful to Surveyor Achinovu and management of ENGEE Survey for making the Bathymetric Survey Report of Kainji Reservoirs (unpublished) Prepared for ROYAL HASKONING Limited October 2006 available.
REFERENCES
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