Data, code and supplementary video of the evolution of a drainage network in the laboratory.

During rain, water infiltrates the soil and accumulates in the aquifer, where it flows as groundwater. When groundwater emerges at the surface with sufficient force, it erodes the landscape and forms rivers. We reproduce this process in a laboratory experiment to investigate how groundwater flow controls the growth of drainage networks. At the same time, we use a numerical solution of the Poisson equation to reconstruct the shape of the water table around the experimental network.

This dataset includes a video of the experiment ; time-series of piezometric, discharge and drainage area measurements ; python code of the numerical solution ; a directory grouping data which describes the shape of the network at three moments in the experiment, necessary to run the python file.

This experiment was built and conducted by Céleste Romon, François Métivier and Eric Lajeunesse at the Institut de Physique du Globe de Paris (2025).

- Video of a drainage network formed by seepage erosion in a experimental aquifer :
This video shows the top view of the experimental aquifer we built. It is made of light plastic sand and has a flat surface. As we inject water through the aquifer, groundwater emerging at the surface erodes grains, which are then entrained towards and out of an outlet on the bottom border (top view) of the experiment. As seepage erosion takes place, channels begin to grow until a drainage network covers most of the aquifer extent. This experimental run lasted 35 days.
This video illustrates how groundwater flow, through seepage erosion, can create a ramified drainage network.

- discharge_measurements.csv
Tabular data file composed of 3 columns and 21 rows. Discharge at the outlet of the experiment, measured by collecting water in a beaker during a fixed duration in time, and then weighing the beaker.
Column 1 : date of the measurement, in format Year-Month-day-hour-minute.
Column 2 : Duration since the first measurement, in days.
Column 3 : Water discharge, in mL/min

- Area_and_discharge.cvs
Tabular data file composed of 3 columns and 11 rows. Estimates of the drainage area measured at 10 moments during an experimental run, and value of discharge at the same time (Figure 4 of the associated publication).
Column 1 : date of the measurement, in format Year-Month-day-hour-minute.
Column 2 : Area of the drainage network in squared meters. This value was estimated numerically by counting - on an image of the experiment - the number of pixels within the drainage area, compared to the total amount of pixels.
Column 3 : Discharge flowing through the experimental aquifer in m3/s, measured at the outlet of the experiment (as defined previously).

- piezometric_levels.csv
Tabular data file composed of 23 columns and 1203 rows. Water level measured every 23 minutes during the experiment from an array of 22 piezometers we installed in the laboratory aquifer. The water level is extracted from photographs of the piezometers.
Piezometer number 1 (n1) is on the bottom right corner of the experiment, and piezometer number 22 (n22) is on the top left. On figure 2 of the associated publication, only piezometers n1 to n18 are represented. On figure 3.b of the associated publication, piezometric data from four piezometers is represented. The corresponding numbers are : A = n2 ; B = n10 ; C = n12 ; D = n18.
Column 1 : date of the measurement, in format Year-Month-day-hour-minute.
Column 2-23 : water level, in cm.

- functions.py
Python code of all the functions we used to reconstruct the water table height in the laboratory aquifer. In particular, this code shows how we solve equation (2) of the corresponding publication, and how we obtain the shape of the water table on figures 5.a and 6.a-c. An example of how to use the functions is added at the end of the python file. To run the file successfully and plot the examples, one must also download the solve_data directory which includes several data files.

To use these functions, several libraries are necessary.
- numpy, matplotlib, scipy and pylab are installable via pip or conda
- pyFreeFem (2024) is available for download at https://github.com/odevauchelle/pyFreeFem/tree/master/pyFreeFem. Using the sys built-in Python module, command sys.path.append() then calls open the pyFreeFem library to where you stored it on your device. It is also possible to call upon the github directly.
- pyFreeFem requires the installation of software FreeFEM++ (2023). The installation guide is available at https://doc.freefem.org/introduction/installation.html

- solve_data directory
This directory groups the data of the numerical mesh we built to represent our laboratory aquifer (nodes, coordinates, triangles). Each mesh is delimited by the borders of the experiment and the shape of the drainage network. Thus, the mesh changes depending on what moment of the experiment we are representing. In this directory, we include 3 subdirectories which each hold data for one specific moment.
This data is needed to run python file functions.py, and reconstruct the shape of the water table in the experimental aquifer at the three moment plotted on figure 6.a-c of the associated publication.
More information about the data is available on the README.txt file in the directory itself.
(2025-01-29)