Storyboard

Since there is currently no availability of public drinking water, an alternative must be sought, such as digging a private well or accessing one shared with several neighbors.

The property has a wetland and, for a good part of the year, a continuous flow of water from a spring that emerges at the top of the wetland. However, during the summer, this source dries up.

>Model

ID:(146, 0)

Description

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The water comes entirely from rainfall collected in the area surrounding the land, extending up to the top of the hills. This area is located 750 meters from the coast and spans a strip of approximately 120 meters. These measurements are conservatively estimated based on the average distance of the wetland area and nearby ditches.

Thus, the total area is approximately 90,000 square meters, and with over 2,000 millimeters of annual rainfall:

This amounts to 180,000 cubic meters of water per year, or an average of 5.7 liters per second.

ID:(905, 0)

Description

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At the southern end of the wetland, at the highest point, there is a spring that flows at about 0.5 liters per second in winter but almost dries up in summer. Therefore, it is important to consider the seasonality of the rainfall, which can be reviewed by the monthly accumulated rainfall:

Assuming that all the rainwater flows to the sea, without considering evaporation loss, it would mean a flow of approximately 23.5 liters per second in winter, compared to only 3.4 liters per second in summer. This indicates that there is seven times more rainfall in winter than in summer. However, when observing images of the wetland at different times, it is noticeable that it does not dry up in summer:

This implies that the water table drops, but not enough to dry out the wetland.

ID:(906, 0)

Description

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If the topographic survey is overlaid with the satellite image obtained from Google Maps, both the wetland area (blue continuous curve) and adjacent areas where water also emerges can be identified. Additionally, a central line corresponding to the center of the wetland (orange line) can be identified:

There are two key points in this representation. The first (1) is the spring that emerges in winter, indicating that the water table is close to the surface at this point. The fact that the wetland area is saturated with water in winter indicates that it is at the water table level, and particularly in the embankment area, there is a significant flow of the water table towards the wetland. This results in the flow at the lower part of the wetland reaching 1.0 liters per second in winter.

The second point of interest (2) is where water emerges but does not flow on the surface, suggesting that the water table is also at the surface level at this point. This should be the original level, and the water table likely descends towards the wetland area due to the water flow.

ID:(907, 0)

Description

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Assuming a homogeneous soil with permeability $k_s$ and a slope length $l$ ($750 , \text{m}$) and a rainfall rate $r$ (in winter $1.3\times 10^{-7} , \text{m/s}$), the height of the water table $h$ at a distance $x$ from the coastline can be modeled as:

$h(x) = l\sqrt{\displaystyle\frac{2r}{k_s}\displaystyle\frac{x}{l}\left(1-\displaystyle\frac{x}{2l}\right)}$

If the curve is fitted to the points of the spring (1) and the water table without the presence of the wetland (2), it is found that the permeability is approximately $4.8\times 10^{-5} , \text{m/s}$, which is represented by the blue line:

According to this, the entire area of the wetland is below the water table height line when the depression does not exist. In fact, the lines of the western edge of the terrain and the height at the house are above the water table level, except in the lower part where the rocks form a type of dam.

On the other hand, it is observed that the house's embankment is above the water table level. If it had reached the water table height, there would have been issues with the stability of the rear wall. Therefore, it is concluded:

When constructing embankments with a wall, it is crucial to identify if there are water tables and their depth to avoid compromising the stability of the structure. This must consider the fluctuations that the water table may undergo throughout the year.

ID:(908, 0)

Description

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In summer, the intensity of rainfall $r$ decreases, causing the water table level to drop. As long as it does not fall more than one meter below the current level of the wetland, it will remain a high-humidity area, preserving its characteristic vegetation:

The images correspond to the wetland during the summer months (January-March), where the greenery is evident. Upon examining the soil, numerous puddles can be found, but there is no noticeable flow (nor can it be heard) as it occurs in winter.

ID:(909, 0)