Evaluation of MAR methods for semi-arid, cold region
Nasanbayar Narantsogt,
Karlsruhe
University
of Technology, Karlsruhe Germany
Abstract:
The semi-arid and cold environment shows a high
variability in precipitation and river discharge. The groundwater aquifer
located near Ulaanbaatar
capital city of Mongolia, is the only source of water supply and it is
important to ensure that groundwater is available now and for the future.
The main watercourse near the city is the Tuul
River, fed by precipitation in the nearby Khentii Mountains. However, due to
the absence of precipitation during winter and spring, the riverbed usually
runs dry during that time, and observations show that the dry period has been
extending within the last years.
However, in parallel with the city’s development,
the extended groundwater aquifer shows a clear decline, and the groundwater
levels drop significantly. Therefore, a groundwater management system based on
managed aquifer recharge is proposed and a strategy to implement these measures
in the Tuul River valley is presented in this paper. It consists of an
enhancement of natural recharge rates during the summer wet period, an increase
of groundwater recharge through melting ice storage in dry period, as well as
the construction of underground dams to accumulate groundwater also surface water
reservoir which release constant discharge in outlet.
The MATLAB icing code written for ice storage on
limited and unlimited area was considered in FEFLOW simulation scenarios as water
source in ice form on surface to increase groundwater natural recharge rates
during the early dry period, through melting ice storages. The study of underground artificial
permafrost as ice dam was processed in FEFLOW simulation scenarios for accumulating
groundwater resources. The results of these artificial recharging methods
calculated individually and combined also compared with surface reservoir which
release constant discharge through dam.
Keywords: Ulaanbaatar, drainage canal, icing, ice
storage, underground dam, reservoir scenarios
1.
Introduction
The Tuul River flows through Mongolia’s capital city
Ulaanbaatar (UB) which originates on highly Khentei mountains upper side of the city. The water level of the Tuul
River fluctuates according to annual high-flow to low-flow cycles, with its
average water flow being 26,6 m3/s. 4.
It also recharges the Ulaanbaatar aquifer that providing city’s
water supply by 218 wells dividing 9 group of intake wells and 21 booster pump
stations of water supply agency, daily domestic consumption fluctuates around
150-200m3/day depends on yearly season. See Figure-1. The company
estimates that another 130.0 T.m3/day is pumped from the aquifer by
private wells run by industries and individuals.
 |
|
a) Mongolian
hydrological drainage basins; b) Tuul River through UB; c) UB water supply
wells
|
The joint meeting of Mongolian and Russian mineral
resources commission estimated the useful capacity of groundwater resources of Ulaanbaatar
aquifer at 264.0 T.m3/day 21,
without upper source lies upper city side from which explore around 24-48T.m3/day
groundwater. 10
As with natural recharging
formation of groundwater resources,
the main balance components are water entering in the aquifer as a result of loss of surface runoff,
and capacitive reserves of the upper water-bearing layer. During the period
from May to December, the aquifer takes recharge due to the loss of the surface runoff at that time. In this period, replenishment infiltrates from the surface water to the stored groundwater capacitive
reserves in the Ulaanbaatar aquifer.
In March and April, the groundwater table of water source
aquifers decreases to a minimum of 8-10 m from the surface, but in June, July
and August reaches a maximum level of 2-3 m under the earth surface in central
source area.9
See Figure 2.
 |
Figure 2. Groundwater table fluctuation depending on
Tuul river flow [12]
|
Water demand increases daily with the development of city
industries and ongoing population growth, but groundwater resource decreases
due to the climate change and excess water usage. In the last decade, during
spring (April and May), the dry period of the Tuul River flow continued longer
than one month after ice breakup.
The following table shows calculated balance with outflow
and inflow at the Tuul River valley aquifer, which is used for the water supply
of Ulaanbaatar city. Tuul River discharge was taken as inflow rate,
precipitation and evaporation amount averaged values over many years. Other
inflow source tributaries to the Tuul River direct to aquifer for the water
supply of Ulaanbaatar draining water
from Selbe, Uliastai
and Khul River obtained over
the last ten years averaged discharge amount, but pumped water amounts from the
sources for water supply city were taken from the year 2010. The balance calculation rate
estimated by subtract total pumped groundwater from the sum of the
inflows-river flows, precipitation and reuse water thermos power plants.
Qbalance=Qinflow-Qpumped+Qreused
Above estimated calculation is considered whole total water
supply upper and city central sources of Ulaanbaatar aquifers with Tuul River
annual average flow rate.
Table
1: Water exploration volume balance for water
supply Ulaanbaatar city
|
Months
|
IV
|
V
|
VI
|
VII
|
VIII
|
IX
|
X
|
XI
|
XII
|
I
|
II
|
III
|
Total
|
|
Balance
[M.m3]
|
10.95
|
79.72
|
125.38
|
216.15
|
231.68
|
135.96
|
42.82
|
5.81
|
-4.23
|
-5.74
|
-5.56
|
-4.76
|
828.18
|
|
sum
[M.m3]
|
848.47
|
-20.29
|
|
||||||||||
The balance for a whole Ulaanbaatar aquifer including domestic
and thermopower plants water consumption is shown above, sorted by hydrologic
years from April where balance takes with positive value.
Total amount of water consumption Ulaanbaatar city used for
water supply in dry, non-recharging season from Tuul river surface water, reaches
about -20 M.m3 depending on from weather conditions and general
precipitation in a given year. This water consumption is pumped from all 9
sources including upper source means balance between income as infiltrated from
the Tuul river and outcome as abstraction rate by intake wells. 19.
This means 20M.m3 explored without recharging from river. The balance estimation between groundwater income
and pumped water for domestic water supply from Ulaanbaatar aquifer source area
without thermopower plants is -7.1M.m3 water.
Therefore, there is an urgent need to solve this problem
through design of hydraulic structures for an
underground dam, managed aquifer recharge and promotion of ice storage or build
surface reservoir dam from which release constant controlled outlet water.
In the next chapter will be considered only for domestic
consumption in the central source area of Ulaanbaatar aquifer. FEFLOW
simulation was taken in the upper central source area A zone where only 23
wells for water supply. See Figure 3.
2.
Materials and Methods
Over the last decade, every spring during the months March
and April, Tuul River dried out or does not flow. Therefore, we need to address
this problem by building a complex of hydraulic structures, establishing
measures for flow control and building artificial groundwater recharge systems
like drainage or flooding area near drink water extraction wells.
This study attempts to find suitable artificial groundwater
recharging methods for the upper part of the central source groundwater
aquifer, encompassing the water supply source area of the Tuul River valley
inside Ulaanbaatar. The Central source of drinking water supply system
established into operation 1959. Drinking water is extracted from 93 deep well
pumps, with 7 booster pumping station. The capacity of source reserve is
114000 m3/day. Nowadays water extraction from 70-80 wells and
its volume reach 87-90 T.m3/day supply to capital city. 10
figure-3.
 |
Figure 3.
Ulaanbaatar aquifer, central source area, simulated area
|
The central source A zone was simulated in FEFLOW
simulation. The upper part of the central source intake area near well-68 takes
recharge from river surface water until January where Tuul River flows under
ice cover. After that period Tuul River freezes until riverbed bottom then
groundwater decreases continue until May. But in western side of the A zone intake
wells area near well-51
recharge comes not only from Tuul river it also recharges from the Uliastai
River therefore recharge takes a place early in May. As shown in graph Uliastai
River flow freezes early in November as a small river due to groundwater
decrease begins from October and recharge begins May depends on melting water
from both rivers. See figure-4.
The groundwater recharging process runs as follows.
In the initial
phase of the non existence of
surface runoff from end of April to early May, its groundwater level maximum decreases are observed. If their value is less than the
flow of the river, then it becomes possible to streaming river downstream.
The icing phenomena is one of the most important parameters
for semi-arid, highly continental climate condition and plays significant role
in hydrological cycle and regime 1) in Mongolia. Icing or ice cover of rivers
and lakes plays cold season for icing continues five to six Months and ice
cover thicknesses reaches 0.8 to 3.2 meters. However, some mountains big rivers
with more slope and bigger perturbation boulders in riffle section stayed open
whole year do not completely freeze along the length.
A small river like Tuul frozen to the bed (2.5 Months) 21
and in the mid of April has not ice cover and some places is dry bed without
flow.
The average date of first ice occurrence on rivers is third
week of October. The freezing of the rivers continues from the end of October
lasts end of December. The ice cover duration averages 145 days. During the
last 60 years, the annual mean air temperature in Mongolia has increased 1.660C
with winter temperature increasing 3.610C, spring-autumn temperature
1.4-1.50C, and summer with no clear trend. Temperature has increased
rapidly in the March, May, September and November and therefore the ice regimes
of the Mongolian rivers has changed. 10
Ice phenology has shifted
by 3-30 days in terms of freeze-up and break-up dates and ice cover duration
has shortened. Maximum ice thickness has also decreased from the 1960’s to
2000. 1.
Generally, for a surface ice cover to become firmly
established, the mean (depth-averaged) temperature of water must be less than 20C,
the daily average temperature must be less than -50C, and the wind
speed must be less than 5m/s. 0.
The Uliastai River one of the tributaries Tuul river originates from Khentii mountains
flows from north east side to south through Ulaanbaatar city contributes Tuul
river in area where water supply wells of Central source for Ulaanbaatar city.
Icing - Aufeis
accumulates during winter along streams and river valley in northern Mongolia where dominates
semi-arid, highly continental regions environments. Here in Uliastai river build ice from
mittle of October until end of December and melting process starting from end
of March until end of April.
 |
The icing dynamics depending on more from groundwater
fluxes, that discharges alongside of main channel. That side springs build ice sheets over
frozen riverbed, where mainstream flows under ice cover. Here considered ice
generating process and icing dynamics from middle of October to end of December
2017.
The main stream is flowing by main riverbed under ice cover
but alongside spring stream is creating ice on the top of ice sheets. This
phenomenon calls icing or Aufeis. Icing
– Aufeis are sheets of stratified ice formed by freezing consecutive water
leaks. 7.
The water flows over existing ice layers. It forms by upwelling of by ground-water
discharge or manmade drainage channels where groundwater discharge is blocked
by ice, perturbing the steady-state condition and causing a small incremental
rise in the local water
table until discharge
occurs along the bank and over the top of the previously formed ice.7
In the beginning of November where river flow freezing from
side benches, spring discharge which have no longer extending energy frozen firstly. After river bed completely freeze and takes
ice cover then spring discharges leaks from under ice or ice hummock while is
increased groundwater head and pressure flows over frozen ice sheets create
next ice sheet.
Groundwater flux coming on earth surface like springs
create over ice top next ice sheet which fills lower ravines and smooths
horizontal even ice sheet.
The groundwater flux
alongside of the river drains through drainage canal built icing phenomena
while springs flow bed blocked by ice and mainstream in main riverbed flows
under ice cover. In this section,
Uliastai River is like gaining stream almost one of third of the flow
discharges abstracts to the groundwater and groundwater come out side springs.
Thus, phenomena create side
springs leakage from under frozen soil which flows over frozen soil and ice
cover streams, fills ravines and lower lands, creates ice sheet on the ice
until river valley would be even same horizon. After that, the average daily
temperature is decreasing under -200C then groundwater leakage
discharge decreases also head and pressure that means groundwater flux in
underground flowing. Also, drained groundwater, spring charge from surface and
groundwater decrease influences for quantity of groundwater amounts. The ice
thickness measurements from 15-th and 30-th of December show that the thickness
of Aufeis sheets not increased.
 |
Such a way groundwater leakage like drained water or
springs over frozen soil and ice cover create stratified ice sheets over ice
sheets. Here in Uliastai river spring discharge 32 l/s small amount of water
but it built ice thicknesses in some place until 1m thick. Some of the rivers make ice sheets to several
meters thick. The end of Aufeis built depends on discharge of Springs and
quantity of Aufeis building river flow usually last decade days of December or
first decade days of January where after longest December night begin colder
days of the year. A bigger river such as Tuul is possible to create Aufeis
until February. Aufeis typically
melts out during summer until end of April sometimes beginning of May and will
often form in the same place year after year. 7.
From this icing ideas
written MATLAB code and thus used for managed aquifer recharge for central
source upper A zone accumulate ice storage due to use melt water for recharge
in dry season.
This aufeis spreading dynamics over ice sheets extending size
decreasing while decreasing air temperature day by day from -5 0C to
-30 0C. The result shows that length of aufeis spreading is 2329m,
widening 458m and 1.54m thick. The code for aufeis had simplified with same
slope along flat area. The following code presents aufeis extending dynamics
when spreading water courted with pipeline levees and from leakage point
to courted pipeline levee 1500m. That’s mean length of ice storage is
only 1500m. see figure 6. The result shows that length of aufeis spreading is
1500m, widening 400m and 2.72m thick, is thicker than unlimited area.
 |
Figure 6: The water supply pipeline connecting wells
to reservoir.
|
The one of artificial recharging groundwater resources is the temporary and
spatial redistribution of surface runoff, in beginning of winter to create ice
formation. Figure 6. The surface runoff that flows over north side of the
central section A zone through filtration channel, will be release water at the
end of canal, thus create ice sheets over frozen sheet again.
There are three types of promoting ice
creation ways in cold region in winter on the ground surface, in the
underground open pit or channel and on the river bed. Two of them surface and
underground ice creation were considered in FEFLOW simulation scenarios. See
Figure 6.
The releasing water amount 1 m3/s
beginning of November until middle of December create icing where days average
temperature decreased under -5 OС.
From the following graph seen that northern
drainage canal allow us to accumulate 1 m3/s flow water for a
month from November to mid December 3.9 M.m3 water to store on
surface. But with losses from evaporation and winter fog over frozen ice sheets
also in melting season evaporation loss allowed only half of this quantity
about 2 M.m3 to accumulate and recharge groundwater.
The melting water from Aufeis begins to flow
and recharge groundwater early April where surface water flows only until
central source area and flows underground.
Therefore, melt water from ice storage, recharge groundwater in central
source A-A zone from north side from beginning of April until May where surface
water flows until end of aquifer.
Ice accumulation from November to end of
December also recharge groundwater while water flows through drainage canal.
Then it is transferred to an artificial regime with the subsequent supply of
water to the canals, functioning together until the period of ice formation,
provided the ice accumulation from surface water on the end of canal.
Aufeis is an icing method bringing more
recharging water in the middle of the study area for its other constituent
subsections, and an ice wall increasing the backside of western boundary. The
drainage canal filtrates through northern side and recharge occupies whole area
from east to west boundary.
The all combination method includes an ice
wall, icing and a drainage canal. The drainage canal filtrates water from east
to west along the north side of the study area and rest released from it water
as early winter creates icing. Thus, this icing method performs after drainage
canal filtration ceases altogether.
As seen in the following Figure, recharge
from the drainage canal begins in May and ends in November, with icing recharge
beginning in the middle of March and lasting May, and the ice wall holding groundwater
in backward from March until November.
In
nature, we can reserve more water in ice form as Aufeis to help build some
hydraulic structures such as a drainage canal or underground dam. Both these
structures can help us to reserve water stores in underground as well as
keeping them on the surface in ice form.
Using coldness and icing in a semi-arid,
highly continental region such as Mongolia can increase groundwater resources.
The nonconventional artificial recharging methods like discussed in this
dissertation, such as ice storage, helps groundwater recharge in dry season,
where there is no flow and dry beds in river systems.
From October to December surface water naturally accumulates and is
kept in ice form from river
flow in the semi-arid,
highly continental region, of the study area. During the subsequent dry season,
these sources increase and recharge potential water availability by melting
water sources.
One possibility is to reserve water
resources
to regulate groundwater flux control in highly continental cold region
to eleminate
dry riverbeds and
keeping primary source rivers, such as the Tuul, continuously flowing during
low flow period by melting ice blocks.
 |
Figure 7.
The all variation combination in simulated area compare to measured groundwater
level
In this calculation of FEFLOW simulation
is taken the maximum differences between simulated in natural condition and
simulation in each managed aquifer recharge scenarios. The result of FEFLOW
simulation in each MAR methods scenarios demonstrates following results:
·
Single ice wall on western boundary alone
in natural condition without drainage canal increases groundwater resources 516
T.m3/year.
·
The drainage canal through northern side
filtrates groundwater around 1 M.m3/year
·
The icing on the end of drainage canal
recharge groundwater resources in aquifer 1.6 M.m3 water
·
The
aquifer additional recharge groundwater quantity of all combined MAR methods is
2.55 M.m3/year. [19]
4.
Discussion
A
preliminary analysis, as presented in this study, was to identify low-cost MAR
implementation measures adapted to the specific natural conditions of Northern
Mongolia. Thus, coldness cold weather can use to keep water in ice form as well
as a water resource in the winter season and be used during low flow dry season
by melting ice where rivers have dried out.
The accumulated ice would be recharging
groundwater in dry season from March to May by melting where is river bed dry
no water any cover ice there.
To find total additional water resource
recharged by Northern drainage canal and Ice storage should increase
abstraction rate until maximum possible rate when GW drawdown decrease under
bottom of wells filter screen, soaks up air.
For a calculation of potential maximum abstraction quantity without MAR
methods in the central source A-A zone, should estimate FEFLOW simulation until
in some well groundwater drawdown reaches bottom of the well screen pump air
instead water. Such a way can establish
groundwater fluctuation ranges in FEFLOW.
The groundwater fluctuation graph of
monitoring well N8 show that, by increasing daily extraction to 60986 m3/day
is could not pump water while groundwater drawdown is under bottom screen. But in the middle of group of wells where
happens extreme drawdown of groundwater level there only 45121 m3/day
is possible. Therefore, maximum abstraction rate of this area is 45121 m3/day,
which means 16469165 m3/year=16.5 M.m3 water
per year.
Nowadays the exploitation rate is (average
of 2009-2011) 20329 m3/day,
7.5 M.m3/year half of possible maximum abstraction.
The recharge quantity with MAR method then
maximum abstraction rate increases until 70133 m3/day means
25.6 M.m3/year.
Difference between above maximum abstraction
simulations show that groundwater resource possible to increase after MAR
methods over extraction rate around 25 T.m3/day. That means
approximately 912500 m3/year=9.125 M.m3 could
additional groundwater during wet season could keep as reserve in this central
source area upper part A-A zone.
The percentage of each MAR methods for a
recharge groundwater resources in this area estimate so that sum of total
amount of all methods is taken 100% from it respectively percentages for each
method.
The percent of increased amount of water
reserve by each method in combination of MAR methods increased groundwater
sources is following.
·
drainage canal brings 73.5 % of artificial
recharging 6.7 M.m3 water (1 m3/s discharge
water through drainage canal from May to November 86400m3/day *
184day=15897600m3=15.9M.m3).
·
Ice storage keeps water in ice form 21% mean
1.9 M.m3 (1 m3/s discharge water for ice
storage would be 5.2 M.m3 but fog and evaporation by icing and
melting brings huge loss)
·
Ice wall, which delays groundwater flux, and
keep groundwater table stable leads to keep 5,65% of increased groundwater. It
is about 516 T.m3 water amount [19].
All
these FEFLOW simulations were simulated in transient model where river surface
water level increases wet season over river bed and dry season decrease under
river dry bed. The eastern and western boundary groundwater table fluctuates under
surface depends on recharge from river yearly.
Another different simulation scenario is for
surface water reservoir with dam from which release water with constant
quantity 26.6m3/s rate and create constant groundwater water table. In this
case taken steady model with eastern and western boundary with constant groundwater
level and hydraulic head also southern boundary as Tuul river with constant level
value to recharge groundwater. The FEFLOW simulation for maximum abstraction rate
reached here 90288м3/day.
After that the simulation demonstrates error report that the aquifer has no
groundwater. Figure 8.
 |
Figure 8.
The groundwater contours and error by pumped groundwater 166700м3/day
|
This
means the flow control by
surface reservoir accumulates flood water and additionally recharge groundwater
quantity for central source A zone is 16.5 mio.m3/year.
The
flow control upper reservoir release constant outflow whole year that means it
also recharge central source B zone, occupying double sized bigger area with 50
intake wells. The whole central source area recharge from reservoir
releasing constant rate would be 49.5 mio.m3/year. Also accumulated
water in reservoir about 350 mio.m3 would be reserved fresh water
resource. All these simulated calculations were recharging water only from reservoir.
When
we are simulating combination of an artificial recharging groundwater sources
and reservoir releasing surface water recharge than additional recharged
groundwater would be 167700 m3/day. See figure 10.
 |
Figure 9.
The groundwater simulated contours by combination managed aquifer methods and recharge
from Tuul river outflowing from reservoir.
|
Figure 9. The groundwater
simulated contours by combination managed aquifer methods and recharge from
Tuul river outflowing from reservoir.
This MAR methods and reservoir recharge
system include following simulation scenarios
·
northern drainage canal recharge groundwater
resource from northern side in wet season
·
ice storage recharge groundwater by melting ice
in dry season
·
until permafrost 5-10 m [5-6] underground ice dam
which accumulates groundwater backside
·
surface reservoir with constant release discharge
in Tuul river which recharge this area from southern side whole year
In this combination scenario possible
maximum abstraction rate is increased to 167700 m3/day after
that simulation. The maximum possible abstraction quantity for year reaches
44,7 mio.m3/year.
Here FEFLOW simulation run only for central
source A zone when we take second B zone with 50 wells this maximum abstraction
rate would be increase at least double 89,5 mio.m3/year because B
zone two times bigger as A zone. If Tuul river flows yearly with constant
discharge, then river surface water will be recharge for industrial source and
that increase additional groundwater resource. This will be increase groundwater
sources 149 mio.m3/year and create natural condition for Tuul
river discontinuously flow that help avoid risk of fresh water supply shortage for
Ulaanbaatar city.
5.
Conclusions
The managed
aquifer recharging methods taken in this simulation variants are northern
drainage canal which recharge groundwater from opposite side as Tuul river, icing or Aufeis keeps water in ice form
brings it from end of wet season through winter to the dry season, increase
groundwater sources by melting, in the end of upper part of aquifer western
side build underground dam which accumulate groundwater backside. All these
variants are in FEFLOW simulated and the recharged quantity were calculated separately
and combined are demonstrated following results.
·
Single ice wall on western boundary alone
in natural condition without drainage canal increases groundwater resources by 516
thousand.m3/year.
·
The drainage canal through northern side
filtrates groundwater around 1 mio.m3/year
·
The icing on the end of drainage canal
recharge groundwater resources in aquifer 1.6 million.m3
water
·
The aquifer additional recharge groundwater
quantity of all combined MAR methods is 2.55 million.m3/year.
[19]
The additional
recharged groundwater difference by increased daily abstraction rate from this
aquifer with and without managed aquifer recharge would be 9.16 mio.m3/year.
When in FEFLOW
simulation scenario has taken surface water reservoir which release constant
discharge flow then recharge from only reservoir separately and combined
simulation with MAR methods calculations demonstrated
following results.
·
The
recharge quantity from the Tuul river with constant discharge entire year 16,5 million.м3/year.
·
The combination MAR and surface water from
reservoir outflow recharges 44,7 million.m3/year.
These simulation results only from upper part with
23 wells of central source area which has total
72 wells. When simulate whole Ulaanbaatar aquifer
then additional recharged groundwater resource from Tuul river flow with
constant runoff would be at least 3 times more than this small area as
150million.m3/year.
The simulation both
transient (MAR methods) and steady reservoir outflow recharge methods show that
groundwater artificial recharge methods not enough for additional recharged
quantity compared to surface reservoir outflow recharging. But combination of both
methods demonstrates more effective for an artificial recharging groundwater
sources in aquifer.
The Tuul river reservoir will be locate upper from
aquifer, would be accumulates 350 million.m3 creates more
humidity environment in Ulaanbaatar region. A positive side effect of increased evaporation from the open water is
that air humidity will be increased which will lead to artificial precipitation
and a deposition of atmospheric particles from air pollution and thus help to
improve air quality in the city and its surroundings.
Groundwater flux
disturbed by the presence of an ice wall come out on surface during spring, spreading,
evaporating and losing some quantity. This makes a fog in winter season and
originates turbidity in air where cold high-pressure cyclone dominates in
Ulaanbaatar city. Turbidity of air makes windy surroundings and clear air
pollution.
This MAR method water storing in ice form in
semi-arid, cold highly continental region, would be also produce coldness 2
during dry season and increase the inner continental hydrologic cycle by
melting and evaporating. In dry season ice melt evaporates and increases
precipitation. Every year in dry season many forest fires occur in Mongolia, at
least partially due to no precipitation and lower air humidity. Therefore,
ice-keeping methods would help us to keep the environment green,
environmentally close to natural process to improve human and natural habitats.
The Aufeis blocks,
icing made in river valley is increasing inner continental cycle by evaporating
meltwater. Thus, it helps to grow up vegetation and increase precipitation in
dry period. During fall months, from
September October, with more rain soil moisture increases and during spring
(March April) there is more humidity in the air and more rain. (by personal
observation.) Meltwater is the mean source for rivers continuously flowing and
recharging groundwater aquifers. Around
the icing area, natural grown bushes and trees as well as designed recreation
areas could renature the environment for the local population.
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