Physical limnology and hydrological regime of two lagoons from the

Physical limnology and hydrological regime of two
lagoons from the South of Spain (Albuferas de Adra,
Almería): hydrogeological consequences
M. Rodr
íguez-Rodríguez1, L. Cruz
-Pizarro2, J. Benavente2, E. Moreno
-Ostos2 and I. de Vicente2
Rodríguez-Rodríguez
Cruz-Pizarro
Moreno-Ostos
1 University
Water Research Institute
ón y Cajal
Institute.. University of Granada. C/ Ram
Ramón
Cajal,, 4. 18071. Granada
2
Lagoon Area (A; hm )
Maximum length
Introduction
(Lmax;
m)
Nueva
lagoon
9,4
27
586
759
Shoreline length (Lo; km)
1,5
2
Maximum depth (zmax; m)
3,19
3,8
0,12
0,63
Catchment area (Ac; hm )
1300
50
Mean width (Bm=A/Lmax; m)
160
357
3
Volume (V; hm )
2
The hydrological regimes of two lagoons from the South of Spain, “Albuferas” Honda
and Nueva of Adra, Almería (figure 1) have been characterized from hydrogeological
and limnological data. Morphometric parameters and the thermal structure of the water
column are coherent with the conceptual model established for this system. The
obtained results from water balances and piezometric measurements around the shore
of the two lagoons suggests a peculiar behavior of the coastal aquifer - in the area in
which the lagoons are located - that could explain the differences in the physical
limnology of the two systems. Finally, the results of a thermal balance calculated from
meteorological data measured with a very fine (2-hourly) temporal resolution reveals a
strong influence of the external factors (solar radiation, wind speed and precipitation)
over the thermal regime (stability of the water column) and, therefore, the ecological
dynamics of the two lagoons.
Honda
lagoon
Mean depth (zm=V/A); m)
1,3
2,3
1/2
1,8
1,2
1/2
Shore development DL=Lo/2(A*p) )
1,4
1,1
zm/zmax
0,4
0,6
138,7
1,8
110,3
0,8
Relative depth (zr=100*zmax/(A*p) ; %)
Ac/A
-1
(Ac/V; m )
Results and conclusions
Morphometric characteristics that distinguish the
lagoons and contribute to explain their ecological
functioning are shown in table 1. The fact that Nueva
lagoon’s area is almost three times bigger than that of
Honda lagoon determines some of the observed
differences in the hydrodynamic and thermal behaviour
between the systems, thus, in this kind of small lakes the
main energy inputs comes into the system throw the
lake surface.
The shore development indicates the potential effects of
the littoral processes in the lake.These effects are not
very important for Nueva lagoon (with an ellipsoidal
shape) but notorious in the case of Honda lagoon (DL =
1.4).
Table 1 Morphometric
characteristics of the systems
studied (Hutchinson, 1957)
One of the most remarkable differences in the morphometry of the Adra lagoons relays in the value
of the Ac/A index. In the Honda lagoon this index is almost one hundred times higher than in the
Nueva lagoon (138.7 vs. 1.7) because of the existence of the above mentioned ramblas that
recharge the former lagoon. This fact contributes to disturb the hydrologic and nutrient dynamics of
both lagoons.
The relation of the basin area with the lake volume (Ac/V) is roughly linked with the trophic
conditions, although eluding important factors such as the basin lithology, soil type or slope. In
Honda lagoon this index is 110.3 m-1 and in the Nueva 0.8 m-1.
“ramblas”
Honda
Adra river
Nueva
r
Ad
a
er
r iv
Figure 1 Hydrological basin of Honda lagoon showing
the three main “ramblas” and the Adra river. The coastal
aquifer in which the lagoons are located is also shown
(right)
Adra
Adra
Methodology
Piezometric level
(m a.s.l.)
3
2
1
0.5
28
26
89
97
104
111
120
127
134
140
6
5
The detailed study of the
24
4
22
3
stratification and water column
20
2
1
8
1
stability (2h-data) and other
16
0
meteorological parameters (solar
1200
2
1000
radiation, air temperature, etc.)
800
1
600
shows a strong dependence of the
400
200
mixing phenomena on
0
0
meteorological conditions (figure 3).
a irtemp.
Air
Radiation
Heating of the superficial water
Rainfall
Pressure
induces a slight stratification during
References
Figure 3 Water column stability related to other
the day. A very fast cooling of the
meteorological data in Honda lagoo n . It can
water column is observed during
- Benavente
Herrera,
J.; Eldue
Amrani
Variaciones de
the last days
of March
to thePaaza, N. y Rodríguez
be notedRodríguez,
the effectM.
of2003.
the “ramblas”
in the
salinidad
en
las
albuferas
de
Adra
(Almería).
Geogaceta,
33.
11-14
pp.
runoff recharge from the “ramblas”,
thermal
structure
of
thisInc.,
system.
- Hutchinson.
1957.
A
treatise
on
Limnology.
Ney
York:
John
Wiley
&
Sons
1015 p.
after a rainfall episode over the
- Idso,
S. B. 1981. A set of equations for full spectrum and 8- to 14 um and 10.5- to 12.5-µm
basin.
thermal radiation from cloudless skies. Water Resources Research 17(2): 295-304 pp.
- Martín Rosales, W. 1997. Efectos de los diques de retención del borde meridional de la sierra de
Gádor (Almería). Ph. D. Thesis. University of Granada. 266 pp.
- Rodríguez Rodríguez, M. 2002. Contribución hidrogeológica y limnológica a la caracterización
ambiental de zonas húmedas de Andalucía oriental. Ph. D. Thesis. University of Granada. 205 pp.
20 cm
60 cm
100 cm
140 cm
188 cm
220 cm
260 cm
300 cm
Temp.
Study site
Figure 2 Sketch showing the hydrological
regime of Honda and Nueva lagoons in two
situations: summer (top) and during a storm
with runoff (“ramblas”) recharging Honda
lagoon (modified from Benavente et al.
2003). E = Evaporation, P = Precipitation, R
= Runoff
2
Groundwater flow in the coastal aquifer
(Adra river delta detritic aquifer, see figure
1) is mainly produced to the coastal
border. Nevertheless, in the area where
the Albuferas are located (south east
border) gradients are very small so little
discharge to the sea is expected as the
major component of the water balance
may be lost by evaporation or by
infiltration to the aquifer. The hydrological
behavior is different in each lagoon as
suggested from the results of the water
balance. Honda lagoon recharges the
aquifer (-328 103 m3 during the study
period) as the main component of the
recharge is superficial water: runoff from
the ramblas, and Nueva lagoon takes the
groundwater discharge from the aquifer
(299 103), thus, the main discharge
component in this system should be
evaporation to the atmosphere, due to its
great water surface. Moreover, depending
on the season the hydrological regime of
the two lagoons is different as can be
observed in figure 2.
Wat. col. stability g-cm/cm
2
Pablo de Olavide. C/Utrera, km 1. 41013. Sevilla
89
97
104
111
120
127
134
140
35
1020
30
1015
25
Water balance and water column stability diagrams were obtained between
1999 and 2003. Groundwater flow was measured from a series of shallow
piezometers installed on the shores of the two lagoons (maximum depth =
3m). Contributions due to the Ramblas were estimated from runoff
coefficients
and FUNDED
rainfall thresholds
(Martín
1997). Meteorological
THIS
WORK HAS BEEN
BY THE PROJECTS:
UERosales,
- LIFE B4 - 3200/98/458;
CICYT HID 99 –
0836
AND were
A9/02 (GENERAL
OF EUROPEAN
AFFAIRS,
CONSEJERÍA
DE LA
data
obtained DIRECTION
from a Squirrel
MiniMet
Weather
Station. Water
PRESIDENCIA, JUNTA DE ANDALUCÍA)
temperature was measured from a series of submerged thermistors (16)
attached to a fixed buoy in the centre of the lake; a Grant Data Logger was
employed to collect the data. Water column stability was calculated from the
equation:
Being ρz = density (g cm-3) at depth z, ρ = average density and zρ = depth at
which the water column have ρ density before mixing (Idso, 1981). Detailed
methodology in the calculations of water and thermal balances can be found in
(Rodríguez-Rodríguez, 2002).
1010
20
15
10
5
R a in fa ll
R a d ia tio n
T . aire (ºC )
R adiac. (W /m 2 )
L luvia (m m )
P resió n (m b )
F ro m m a rch 3 0 (ju lia n d a y 8 9 ) to m a y 2 0 , y ea r 2 0 0 1
T em p .
1005
1000
995
P ressu re