post-aswan dam sedimentation rate of lagoons of the nile...
TRANSCRIPT
Post-Aswan Dam sedimentation
rate of lagoons of the Nile Delta,
Egypt
Jiawei Gu1 , Zhongyuan Chen1, and Alaa Salem2
1 State Key Laboratory of Estuarine and Coastal Research of ECNU, China2 Geology Department, Kafrelsheikh University, 33516 Kafrelsheikh, Egypt
On-going Project
This joint work aims to trace the sedimentation
rate and examine the concentration and transfer
processes of heavy metals in both estuaries
A comparative study on spatial and temporal
distribution of heavy metals in the Nile and
Yangtze coastal wetlands – the special reference
to ecological safety
Location
Map
Mediterranean Sea
Cairo
N i l e D e l t a
Remarks from Earlier Research
Lagoons of the Nile Delta have experienced more
pollution after the construction of Aswan high dam in
1964 as evidenced from its heavy metals concentration
and high TOM.
Sedimentation rate from low resolution coring ranges
from 0.20~0.56 cm/yr by 210Pb , 137Cs.
The upper 10-15 cm sediment was deposited after the
construction of Aswan High Dam in 1964.
Pb, Sr, Mn, Zn, and Cd are the main pollution metals.
• To examine the sedimentation rates in the
Nile Delta lagoons, particularly since
completion of the Aswan High Dam in 1964
based on high-resolution coring (1cm interval)
• To reconstruct the pollution history and
analyze the controlling mechanism
Objectives
• How does the post-dam depositional process act
in the Nile Delta ?
• What are the heavy metals distribution and
dispersal pattern in the lagoons of the Nile delta ?
Research Questions
Amounts of sediments transported into the Nile before and after Aswan
Damming (Data recorded from gauge station at Rosetta Promontory)
0
500
1000
1500
2000
2500
3000p
pm
ينايرفبراير
سمار
ابريل
مايويونيه
يوليوسأغسط
سبتمبر
أكتوبر
نوفمبر
ديسمبر
قبل السد العالى After DamBefore Damبعد السد العالى
Jan.Dec.
Study area
East Asian
Monsoon RegionStudy
Area
Edku
Burullus
Manzala
The Nile Delta
Materials and Methods
Heavy metal
analysis for six
cores using the ICP
Three sediment
cores were analyzed
for Pb210 and Cs137
using a high-purity
germanium well-type
detector
Granulometric
analysis was done
to determine the
proportions of
sand, silt, and clay
Sedimentation rate on the Nile Delta
CIC (Constant Initial Concentration) and the CRS (Constant
Rate of Supply) model were commonly used to calculate
sedimentation rates using 210Pb (Appleby and Oldfield 1983).
Sediment lithology of the three cores
Core M-1 coarser sediment with some
shell fragments (0–10 cm) and the finer
sediment with a few shell fragments
(10–25 cm)
Core B-4 exhibits remarkable
variations in sediment composition in
which four sediment sections could be
identified
Core E-1 shows more homogeneous
sediment composition
Depth distribution of ex210Pb
(CIC model) and 137Cs in the
three short sediment cores
~10 cm thick sediment deposited
after the Aswan damming in 1964
This low sedimentation rate (0.22-
0.27) is a consequence of dramatic
reduction in sediment load as a
result of damming
The 137Cs spikes at the core depth of
9.5 cm of B-4 and of 4.5 cm of E-1
helped identify the sedimentation
rates of 0.22 cm a-1
Exponential decline in ex 210Pb in
the upper section of M-1 and E-1 is
noticed showing a sedimentation
rate of about 0.27 cm a-1
Sedimentation rates revealed by the CRS model and
area loss of three lagoons during 1950–2010
The pre-dam sedimentation rates of this study in Manzala were relatively high,
around 0.5 cm a-1, but lower in Burullus and Edku at around 0.1–0.2 cm a-1,
compared with the results from previous studies of around 0.2–0.8 cm a-1
The sedimentation rates in Manzala dropped to 0.1–0.2 cm a-1 after the
completion of Aswan High Dam in 1964, and persisted for about two decades while
Burullus and Edku showed a slightly increasing trend
Heavy metals distribution of the Nile Delta
Upward increasing concentrations (Normalized) of most
heavy metals correspond well with the time of damming
(~10cm ) Ensuing large-scale industrialization
Spatial distribution of
heavy metals in Manzala,
Burullus, Edku
M-2>E-1>E-2>M-3>M-1>B-4
Controlling factors (in order
of importance):
• Wastewater type
(industrial>agriculture/sewage)
• Distance to the drain outlet
• Dispersal pattern
( prevailing wind and currents)
• Sediment type
(finer>coarse)
Contamination
Factors of six cores
(CF=surficial
/background value)
Most enriched metals:
Pb, Sr, Mn, Cu, Zn, Cr
Human activities and pollution process of heavy metals between the Yangtze Delta and Nile Delta
Concluded Remarks
This high-resolution radiometric study using short sediment cores
has essentially revealed the post-Aswan dam sedimentation of the Nile
lagoons.
There have been lower sedimentation rates ranging from 0.22 to 0.27 cm
a-1 as illustrated by 210Pb (CIC model). The results highlight the general
situation of post-dam sedimentation in the Nile lagoons due to the
impoundment of sediment in the reservoir since the 1960s.
However, using the CRS model, we have demonstrated a decreasing
trend of sedimentation rate during 1960–1980s, but increasing trend
since the late 1980s.
The post-dam sedimentation rates of the present study provide insights
into future, better coastal management.
Thanks for your attention!