الفهرس 
Application of numerical groundwater models for groundwater development and managementOnly 14 pages are availabe for public view
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Abstract
Due to the nature of the reservoirs of Nile Delta in Egypt and its valley which are composed of
several successive alluvial deposits, there are many silty clay layers with very low permeability
which can be found with different depths all over the reservoirs. The existence of the low
permeability layers hinders the recital flow of water between the water bearing formations of the
aquifer system and arising many environmental problems such as water logging, water mounding and
pollution.
In Egypt there are many aquifer systems of which the Nile Delta aquifer is considered as one of the
most important aquifers. However, there are several environmental problems such as salinization,
water pollution, logging and mounding of groundwater levels affect the development in eastern Nile
Delta region. In order to overcome these problems and mitigate their negative impact on
environmental and development projects, intensive studies should be carried out. These studies are
morphological, hydrological, geological and geotechnical studies which define the factors affecting
groundwater flow and water pollutions in the aquifer system.
The present research concerns with the water mounding and logging problems in highly heterogeneous
aquifers in new cities. These problems are existing in many areas such as the eastern Nile Delta
aquifer which is adjacent to and connected with the Delta aquifer system, where water logging and
mounding appear in many places especially in El-Obour city and El-Shorouk City.
The objectives of this research are to Study the water mounding and logging problem with
preventative case study, define the sources of problem in the case study area, clarify the
different conditions lead to water logging and mounding, simulate and calibrate the groundwater
flow, and to propose a solution that should be technically and environmentally feasible.
The region of concern in this study is El-Obour City which is located about 25 km Eastern of Cairo
and lies on the hydrologic basin of Heliopolis. It comprises part of the desert area to the east of
the Nile delta and covers about 200 Km2. Due to the low permeability of some layers and the leakage
from water networks and the seepage from the green areas near to the city the 6th and 7th districts
suffered of the groundwater levels rise and logging. Vertical drainage wells were
suggested to drain water from the higher layers to the lower layers which have more permeability.
However, the optimum number of the drainage wells is one of the big issues in such projects for the
practical point of view and for economic purposes.
In order to simulate the study area and the existing conditions a simulation package of Ground
modeling system (GMS 7.1) was used to simulate the study area for practical application in ground
water flow. GMS is the most complete, and user-friendly, modeling environment for practical
applications in three- dimensional groundwater flow and contaminant transport simulation. This
fully- integrated package combines powerful analytical tools with a logical menu structure.
Easy-to-use graphical tools. The model input parameters and results can be visualized in 2D
(cross-section and plan view) or 3D at any time during the development of the model or the
displaying of the results. For complete three-dimensional groundwater flow and contaminant
transport modeling, MODFLOW is the best software package available. The vertical drainage wells
were represented by large vertical hydraulic conductivities with respect to the horizontal
conductivities. It was concluded that the ratio of horizontal hydraulic conductivity per vertical
hydraulic conductivity (kh/kv) should not be less than 0.1, because beyond this ratio value there
is no DROP in the water level.
In order to select the optimum number of wells, five different scenarios have been applied with
various numbers of wells to select the best economic solution. Numbers of wells in each scenario
are changed. The optimum number for the drainage wells were select so as to be the minimum number
after which the groundwater levels do not change significantly. A number of 35 wells distributed
over the modeled area of the 6th& 7th districts, and then started to reduce the number of wells and
observe the effect of this issue on the water level (35, 30, 27, 24, and 20 wells). The optimum
number is that less number of wells which give a suitable DROP in water levels, where the level
after that start to be the same. it was noticed that when the number of wells are more than 27
wells, the DROP in the water levels increases but the ratio of DROP is less than 5%, which means
that increasing the number of wells more than 27 wells does not affect the DROP in water level
significantly. So 27 wells are considered the optimum solution and it is recommended to be
implemented in this area.
New technique has been used to simulate a vertical perforated pipe in MODFLOW by using Conduit Flow
Process (CFP), a model was used to simulate the vertical drainage wells as a proposed solution.
When the model
operated in Mode1 it couples a discrete conduit network to the matrix and uses the Darcy-Weisbach
equation to simulate turbulent flow and the Hagen- Poiseuille equation for laminar flow in the
conduit network. Fluid exchange between the matrix and the conduit network in CFP Mode1 is
considered with an iterative head dependent flux between the conduit network and matrix.
CFP Mode1 considers the conduits as pipes and required some information about the pipes diameter
then can simulate the exchange between the matrix and these pipes. The conduit flow process for
MODFLOW-2005 (CFP) has the ability to simulate turbulent or laminar groundwater flow conditions by
coupling the traditional groundwater flow equation with formulations for a discrete network of
cylindrical pipes (Mode1, CFPM1). Several techniques have been used to simulate a vertical
perforated pipe in MODFLOW, which drains water from upper layer to the lower one. Despite of the
approximated results, there are several questions still have no answers: how does pipe diameter can
affect the recharging head and mounding height, what is the flow type inside the perforated pipe
(Laminar or turbulent). In order to find out the solution of all the previous questions,
ground-water was exchanged between MODFLOW and the perforated pipe network, and correcting
ground-water exchange between MODFLOW and the perforated pipes due to partially or completely
filled pipes. (Rate of filling the pipe from the upper layer may be different than the out filling
to the lower one).A Conduit Flow Process (CFP) model was used to simulate a vertical perforated
pipe in MODFLOW, which drains water from upper layer to the lower one by using Conduit Flow Process
(CFP).
After Set parameter guidance for applying CFP code for drainage problem: Parameters such as pipe
diameter, wall conductance, and penetration length which will influence the exchange of flow
between matrix and the perforated pipes. It was concluded that parameters such as pipe diameter
(pipes with 15& 30& 40& 50 and 60 cm diameter, and wall conductance equal 0.001) which will
influence the exchange of flow between matrix and the perforated pipes.
It was proved that the increase of diameter more than 30 cm not effect on the DROP of water level
on upper layer according to increase the time.
The results of the DROP in the water levels and the water budget by CFP are identical with the
results of GMS.