Post on 18-Aug-2020
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The Dead Sea: mass and energy balances
Nadav LenskyGeological Survey of Israel
Suggested solutions:1. Leave as is2. Release freshwater3. Introduce seawater
Dead Sea level1800-2002
Current rate -1 m/yrCurrent level -417 m bsl
The consequences (environmental etc.) of these alternatives are not clear
The DS level drop –severe
environmental and ecomnomical
consequences
Expected results of mixing seawater with the Dead Sea brine:
Change of the Dead Sea composition with time
Gypsum precipitation
Dilute upper water layer
Microbial blooming in the upper layer
Reduction conditions in the lower layer
Examination of the consequences of the different alternatives usingcomputer simulations
Balances 0-D this lectureDynamic 1-D P.O.M
limnological 2-D W2 qualmodeling 3-D P.O.M
Mass and Energy Balances
Salt precipitation Evaporation
Total mass balance
Water inflows
Measured data:(T, P & RH) - air, SW radiation
(T, P & salinity) - water, water level
Energy balanceSalt mass balanceHeat of evaporation
Measured data:(T, P & RH) - air, SW radiation
(T, P & salinity) - water, water level
Dead Sea Level )1990-2001(
-416
-414
-412
-410
-408
-40690 92 94 96 98 99 01
Level bsl(m)
Year )1/1(
Hydrological service
Level drop ~ 1 m/yrArea ~ 650 km2
Deficit ~ 650 mcm/yr
Hydro-meteorological buoy in the Dead Sea(Gertman I. from IOLR)
(T, P & RH) - air (T, P) - water SW radiation
30 m
20 m
1 m
2224262830323436
0 100 200 300
T (C °)
J Day)after 1/1/1998(
Water temperature at different depths
Overturn Winter cooling
Warm upper water layer
Hydrographycal profiles (T , salinity, ρρρρ)Every 2 months
Bottom at ~300m
T(C)0
100
200
300
22 27 32
Winter Summer
Hydrographycal profiles (T , salinity, ρρρρ)Every 2 months
From IOLR website
Measured annual changes:Surface level drop ~ 1 m / yr
Temperature increase ~ 0.2-0.3 °C / yrSalinity increase ~ 0.3 g/kg / yr
Mass and Energy Balances
Salt precipitation Evaporation
Total mass balance
Water inflows
Measured data:(T, P & RH) - air, SW radiation
(T, P & salinity) - water, water level
Energy balanceSalt mass balanceHeat of evaporation
Total mass balance
Salt precipitation
evaporationpumped
End brinesSubsurface inflows
DS worksSurface inflows
tws Vmm ρ=+
At a given time:Mass of water + mass of salts = total mass of brine
After some time ∆t...
Total mass balance
( )( )slt
rpseiws
VVVmmmmmmm
∆−∆−∆+=
=∆+∆−∆−∆−∆++
ρρ
Total mass balance change during ∆t in:Mass - ∆m
Volume – ∆V Density - ∆ρ
∆∆∆∆mi
∆∆∆∆me
∆∆∆∆ms
∆∆∆∆mr
∆∆∆∆mp
( )( )slt
rpseiws
VVVmmmmmmm
∆−∆−∆+=
=∆+∆−∆−∆−∆++
ρρ
Salt precipitation
evaporation
Total mass balance
pumped
End brines inflows
Salt mass balance Vt
ρS
volumedensitysalinity
( )( )ρρ
ρρρρρ
ns
prrrttls S
VSVSSVVVSSV
−
∆−∆+∆−∆−∆∆+=∆
2 unknowns remain:
Freshwater inflows ∆∆∆∆Vi
Evaporation ∆∆∆∆Ve
salt precipitation
~0.1 m/yr
After ∆∆∆∆t - a year∆Vs, ρs
∆Vl
Vt-∆Vl-∆Vsρ+∆ρSn=S+∆S
After a yearpresent
Mass and Energy Balances
Salt precipitation Evaporation
Total mass balance
Water inflows
Measured data:(T, P & RH) - air, SW radiation
(T, P & salinity) - water, water level
Energy balanceSalt mass balanceHeat of evaporation
?
Net LWEvaporative
heat fluxConductive
heat flux
Net solar
QSN -QLW -Qe -QCQn=Net heat flux
Energy balance
?
e
ee L
Qthρ
∆=∆
From heat to rate of evaporation
AVh e
e∆
=∆
Le - latent heat
( ) ( )asasb
nLWSNe eeTTc
QQQQ−−+
−−=
1
Heat of evaporation (Bowen 1926)
Evaporation rate vs. QLW
Stanhill (1994): 1.05 m/yrSalameh & El-Naser (2000): 2 m/yr
( ) ( )asasb
nLWSN
e
e
eeTTcQQQ
Lt
h
−−+−−∆
=∆
1ρ
Mass and Energy Balances
Salt precipitation Evaporation
Total mass balance
Water inflows
Measured data:(T, P & RH) - air, SW radiation
(T, P & salinity) - water, water level
Energy balanceSalt mass balanceHeat of evaporation
?
( ) ( ) XeeTTc
tThCQQLAtV
asasb
tpLWSN
ei +
−−+
∆∆−−∆=∆
1ρ
ρ
( ) rw
rt
wpl
ws
w
s VVVVVX ∆−∆
+∆−∆−∆−
=ρρ
ρρ
ρρ
ρρρ
Energy and mass balances
Min. observed
Rate of evaporation and inflows vs. QLW
Min. observed
Summary
Salt precipitation Evaporation
Total mass balance
Water inflows
Measured data:
Energy balanceSalt mass balance
Heat of evaporation
Total:265-330 mcm/yr
1.15 m/yr0.1 m/yr
Unobserved:0-60 mcm/yr
Total observed inflows >265 mcm/yr
Thank you…