Figure Legends
Figure 1. Schematic representation of five mechanisms involved in the
partition of the water inputs received by catchments towards
transpiration and streamflow. The top panel shows three ways in which
plant uptake and transpiration takes away water from streams. The first
one (mechanism 1) involves the most acknowledged process of uptake from
the unsaturated zone. The second one (mechanism 2) incorporates uptake
from the saturated zone or the capillary fringe above it in focalized
wetland and riparian areas with a closer contact between plant roots and
water tables. The third one (mechanism 3) encompasses distributed uptake
from the saturated zone or the capillary fringe in the matrix of the
catchment. The second panel illustrates processes by which streams can
take away water from plants reducing transpiration and enhancing stream
flow. They include deepening streambeds (mechanism 4), which enhance
hydraulic gradients and limit plant access to water tables in low areas
or even in the matrix of the landscape; and burying riparian and wetland
vegetation with sediment deposits (mechanism 5) which temporarily
reduces transpiration in those highly transpiring zones.
Figure 2. The developing catchment of El Morro in Argentina. A. Map of
the catchment illustrating the location of the major sub catchments as
defined by their topographic limits, active permanent streams, and
potential drainage lines. Groundwater monitoring sites, which in some
cases include several wells, and meteorological stations are indicated.
The dotted white frame shows the limits associated with the schematic
view on the right. B. Scheme of new permanent streams indicating their
period of formation (also referencing vanished or dead-ended segments).
The area occupied by wetlands and sediment deposits is depicted together
with the location of streamflow measurement points corresponding to the
present study or to previously available records. The Quinto river is
the pre-existing permanent water course receiving the new streams with a
mean discharge of 5.5 m3 s-1.
Figure 3. Decadal groundwater level trends in the El Morro basin. The
twenty seven sites are grouped according to their corresponding
elevation belt within the catchment (higher > 700 m,
intermediate 700-550 m, lower 550-500 m, terminal plain < 500
m). A zero level is assigned at the time of the first measurement in
order to highlight the absolute level shifts starting from that point.
Dotted lines illustrate periods and sites in which incisions were carved
less than 500 m away or where sediment was deposited right on the
location. Mean level changes per decade were calculated excluding the
incision/deposit situations. All sites correspond to water wells used
for ranching whose static level was recorded in the past. In 11 of them,
modern levels were measured directly in the same well or in a new ad-hoc
borehole whereas in the rest levels (always < 1.5 m) were
estimated by the presence of wetlands or lagoons.
Figure 4. Schematic transverse vertical cut of the Quebrachal and Río
Nuevo sub catchments. The transect corresponds to the transition between
the higher and intermediate belts (-33.464, -65.475 to -33.409 and
-65.305, see Figure 2). The surface of the terrain corresponds to the
central transect while belowground features were obtained using
observation less than 600 m away from the transect. Depth of the
crystalline basement comes from vertical electrical sounding (Barbeito
2008) and the old water table level from the long-term observation sites
(Figure 3). The new water table level is reconstructed based on those
same sites and landscape features like wetlands, lagoons and incisions.
An aerial photograph together with google earth imagery were used to
indicate the year of the advent of these landscape features.
Figure 5. Water table depth in 14 monitoring wells at the El Morro
catchment. Levels were manually measured in hand augered wells. The
locations of each pair or group of sites and their corresponding
vegetation and relevant neighboring features are shown accompanying each
plot. Dual numbering in the Y axes is color-coded like the markers in
the plot and used to capture depth offsets between wells using an
identical scaling across all plots.
Figure 6. Vegetation greenness, precipitation and water table depth
dynamics for two periods of 84 days with contrasting hydrological
conditions (recharge vs. discharge) at site A. Greenness is represented
by an 8-day MODIS product, precipitation was recorded at the site and
water table levels where measured with pressure transducers. Note the
color-coded numbering in the Y axis matching the line color of each
stand (green=wetland, black=5-day moving average in wetland,
red=cropland). Grey zones represent the subperiod zoomed at the bottom.
Figure 7. Vegetation greenness, precipitation and water table depth
dynamics for the whole study period in neighboring wells at site C
(cropland and forest at position 2). Greenness is represented by an
8-day MODIS product, precipitation was recorded at “Coronel Alzogaray”
meteorological station, 15 km away, water table levels were measured
with pressure transducers. At the cropland an early gap on sensor data
was filled with manual measurements (red dotted line). Note the
color-coded numbering in the Y axis matching the line color of each
stand (black=forest, red=cropland). Light grey bands depict each growing
season while darker grey bands represent the subperiod zoomed at the
bottom.
Figure 8. Base flow at different locations within the El Morro
catchment. Grey areas depict isolated measurements before the continuing
monitoring program started. Site location and baseflow synthesis are
presented in Figure 2b and Table 1.
Figure 9. Greenness trends at sites with contrasting vegetation
types/trajectories in El Morro catchment. NDVI from Landsat imagery for
areas occupied since the beginning of the period by forests (n=11),
croplands (n=16), and wetlands (n=20) where compared with areas
experiencing the transition from croplands to wetlands (n=14) and
fluvial deposits (n=7). A single case of wetland drying (site B) is also
depicted. Alternate white and grey bars highlight successive growing
seasons and letters indicate significant differences within years based
on ANOVA. The lower panel shows mean monthly precipitation for the whole
catchment and its 12-month moving average. The erosion episode took
place in February 2015.