Hydrogeological Comparison of Three Wells with a Basin Approach in the Nandaime-Rivas Aquifer, 2021 ()
1. Introduction
The main sources for use for irrigation are surface and groundwater. Therefore, the protection and sustained use of the water resource contained in the hydrological unit, is important; therefore, “knowledge of the availability and hydrodynamics of aquifers is a tool that contributes to the strategic planning of management and management of water resources” [1].
The hydrogeological analysis will be done with a basin approach, and according to its origin, for this case, the Dolores 01, Dolores 02 and Mecatepillo sources will be studied, which are underground sources located at the following coordinates: East 610561, North 1292576, East 610234, North 1293090 and East 611482, North 1293881 respectively according to the UTM WGS-84 Zone 16N system.
According to [2], for the year 2004 a good inventory was carried out in the Nandaime-Rivas aquifer, both drilled wells and excavated wells, totaling 124 wells.
He continues to state [2], that the groundwater flows are variable depending on the place, the demand and the potential of the aquifer, and that in the southeastern area the values range between 8 to 341 m3/h, likewise in the southeast zone from 136 to 314 m3/h. In the northeast, it varies from 24 to 296 m3/h.
To verify the analysis of [2], the study of three wells was carried out as an underground source with a basin approach in which a hydrogeological comparison is integrated into a said aquifer.
For the hydraulic characteristics of the aquifer, information was obtained from pumping tests of 44 wells from the files of the INETER Hydrology Directorate and from pumping tests carried out in the study.
In the southeastern part of the area, the transmissibility values vary between 128 to 1132 m2/day, distributed in Las Mercedes, El Peludo, and Rio Chiquito. In the center of the town of Nandaime, Finca el Paraíso, the values found are from 620 to 2000 m2/day.
Likewise, in the southeastern part of the area, the values range between 128 to 1132 m2/day, located in the Los Porvenires, El Paraíso, Candelaria dam, Las Conchitas, etc. In the northeastern part of the area, these range from 368 to 2144 m2/day. In Barrio la Orilla, la Barranca, Los Ranchones, San Felipe farm, el Carmen.
Likewise, in the southeastern zone in the town of La Hormiga, San Rafael, there is no information on wells. In this case, the range with geology 1 < T < 10, called LOW, was determined.
Geographical Location of the Study
Specifically, the study of underground sources is located at km 77 of the Rivas Nandaime road, 1 km to the east. According to the hydrographic basins of Nicaragua, the sites of interest are circumscribed within the 69 Rio San Juan basin, at an elevation of 68.8 meters above sea level for Dolores 01, 67.7 meters above sea level for Dolores 02 and 67.9 meters above sea level for Mecatepillo, the coordinates of the points are East 610561, North 1292576, East 610234, North 1293090 and East 611482, North 1293881. See Figure 1.
2. Methodology
Kind of investigation
The research design is quantitative since the hydrogeological behavior of three wells was analyzed through the hydraulic characteristics in the Nandaime-Rivas aquifer in the year 2021.
Execution time
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Figure 1. Location of study points. Source: [3].
The development of the research, to meet the proposed objectives, was carried out in a single time, in a month of work, a day of data collection, 15 days for data analysis and 15 days to present results in the June period to July 2021.
Data Collection Techniques and Methods
Primary Sources
Solano, E. P. (2005). Disponibiidad y Aprovechamiento Sostenible del Acuifero de Nandaime. Managua: Centro Para la Investigación en Recursos Acuáticos de Nicaragua (CIRA/UNAN).
INETER, ANA, & UNI. (2016). Cuencas Hidrográficas de Nicaragua bajo la metodología Pfafstetter. Obtenido de Cuencas Hidrográficas de Nicaragua bajo la metodología Pfafstetter: http://www.cira.unan.edu.ni/wp-
Peña, E. (agosto de 2005). Disponiblidad y aprovechamiento sostenible del acuífero de Nandaime.
TECNORIEGO, S. (2015). Informe de la Perforacion del Pozo Llano Bonito 1, CASUR. Ochomogo, Nandaime, Granada.
TECNORIEGOS, S. (2017). Prueba de bombeo pozo “Mecatepillo 08”. Managua.
Badillo, J., & Rodriguez, R. (2008). Mecánica de Suelos: Tomo 1, Fundamentos de la mecánica de suelos. México, D.F.: LIMUSA.
Secondary Sources
Library of the National Autonomous University of Nicaragua, Managua (UANA-Managua).
Library of the National University of Engineering (UNI).
Center for Research on Aquatic Resources of Nicaragua, Managua (CIRA- UNAN-Managua).
Archives of the National Water Authority (ANA).
Universe
They are all the underground waters of Nicaragua, that is, all the aquifers including the Nandaime-Rivas aquifer.
Sample
It will be the Nandaime-Rivas aquifer, specifically the three wells described above, Dolores 01, Dolores 02 and Mecatepillo
Inclusion criteria
Underground water sources,
The sources belonging to the Nandaime-Rivas aquifer.
Exclusion criteria
Surface water sources,
Sources that do not belong to the Nandaime-Rivas aquifer.
Hydraulic Characterization of Groundwater
According to [3], the hydraulic characterization of groundwater is listed in the following ways:
Transmissibility
It is the amount of water that an aquifer transmits through the entire saturated thickness in a unit area per unit of time (t). [4] and [5]
It is determined from the following expression:
(1)
where:
Q = flow rate in m3/day,
ΔS = Drawdown drop in m.
To determine the transmissibility of the aquifer, it is done from Table 1.
Hydraulic Conductivity (K)
The hydraulic conductivity is related to the saturated thickness tested, also considered as the volume of gravific water that percolates during the unit of time through a surface unit of a section of land under a hydraulic gradient equal to the unit [8]
(2)
where:
T = Transmissibility m2/day,
M = Tested saturated thickness.
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Table 1. Coefficient, class, denomination of transmissibility.
Source: retrieved from [6] and [7].
Determine the hydraulic conductivity of the aquifer, is done from the following Table 2.
Storage Coefficient
[9] and [10] It is dimensionless. It refers to the volume that the aquifer is capable of releasing when the piezometric level (or pressure) drops by one unit. It is defined as the volume of water that can be released by a vertical prism of the aquifer, with a section equal to the unit and height equal to the saturated thickness. The result corresponds to 0.01
Specific Capacity
[11] The specific capacity is the relationship between the flow rate and the saturated thickness.
Radius of Influence
[11] The radius of influence is the distance that the cone of depression reaches in the aquifer, when a well is pumped for a given time (t). The result depends on the transmissibility (T m2/day) and the storage coefficient (S-dimensionless unit).
(3)
where:
T = transmissibility in m2/day;
t = pumping time in hours;
S = Storage coefficient.
One way of characterizing the aquifer from the radius of influence can be seen in the following Table 3.
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Table 2. Hydraulic conductivity rating.
Source: retrieved from [6] and [7].
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Table 3. Aquifer operation as a function of radius of influence.
Source: retrieved from [6] and [7].
Material and methods
For the hydraulic analysis, the base information provided was provided on the gauged flows in the Dolores 01, Dolores 02 and Mecatepillo 08 sources, currently in use for irrigation; the calculation will be done individually to have a better appreciation of the use of the resource in the basin, with its respective hydraulic characteristics.
A single calculation methodology will be carried out since the same procedure is extended to the other wells; only the synthesized results will be presented.
Step 1: determination of transmissibility, with ecaution 1;
Step 2: determination of Hydraulic Conductivity, ecuation 2;
Step 3: calulation of Storage Coefficient and Specific Capacity;
Step 4: calculation of Radius of Influence, with ecuation 3.
3. Results
Table 4 summarizes the flows, depths, descent and diameter for each well studied.
Tables 5-7 describe the hydraulic characterization of each well.
Flow Versus Thickness
See the following Graph 1
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Table 4. Results of flows, depth, descent and diameter.
Source: self-made (2021).
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Table 5. Hydraulic characterization of the wells under study.
Source: self-made (2021).
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Table 6. Hydraulic characterization continued.
Source: self-made (2021).
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Graph 1. Thickness trend as a function of flow. Source: self-made (2021).
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Table 7. Continuation and final hydraulic characterization.
Source: self-made (2021).
According to the graph, it is shown that there is a relationship between the flow and the thickness of the drawdown; this correlation is equal to 0.991. This means that by obtaining the flow, the thickness of the aquifer can be determined with the linear trend equation obtained.
Flow Versus Transmissibility
See the following Graph 2
The graph shows a trend of the negative slope, which is interpreted as, the higher the volume measured in the place, the lower the transmissibility, always maintaining a correlation of 0.9816.
Flow Versus Hydraulic Conductivity
See the following Graph 3
The graph shows a trend of the negative slope as well as the transmissibility with the flow, which is interpreted as, the higher the flow gauged in the place, the lower the hydraulic conductivity, always maintaining a correlation of 0.993.
Flow Versus Radius of Influence
See the following Graph 4
According to the results of the comparison of the hydraulic radius with the flow, a low correlation of 0.499 is manifested. In a speculated way, the result is due to the type of soil found in the area, if the use of the linear trend equation is recommended, discretion for well study purposes.
4. Analysis of the Results
Regarding the flow versus the thickness, this presents a high correlation of 0.991, with a linear trend with a positive slope; that is, as the flow increases, the thickness of the depletion cone also increases, and this can be adjusted to y = 0.0004X − 1.6679.
With the comparison of the flow versus the transmissibility, this presents a high correlation of 0.9816, with a linear trend with a negative slope; that is, as the flow increases, the transmissibility decreases, and this can be adjusted to y = −2.0149X + 13,090.
Continuing with the comparison of the flow rate versus the hydraulic conductivity, this presents a high correlation of 0.993, with a linear trend with a negative slope; that is, as the flow rate increases, the hydraulic conductivity decreases, and this can be adjusted to y = −0.0818X + 527.45.
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Graph 2. Transmissibility trend as a function of flow. Source: self-made (2021).
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Graph 3. Hydraulic conductivity trend as a function of flow rate. Source: self-made (2021).
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Graph 4. Trend of the radius of influence as a function of the flow. Source: self-made (2021).
Finally, the comparison of the flow versus the radius of influence presents a low correlation and is equal to 0.4999, with a linear trend with a negative slope; the use of the adjustment equation is left to discretion, probably with more data on the site will approach a high correlation.
5. Conclusions
The hydrogeological analysis of the hydraulic parameters of the Nandaime-Rivas aquifer was carried out with a basin approach; the flow was compared with transmissibility, drawdown thickness, hydraulic conductivity, and the radius of influence.
The comparative trend of the result, gave as a result the linear for all the parameters, in comparative relation of the flow with the thickness of the drawdown, this gave a positive slope, with the other parameters it gave a negative slope, but with high correlations. With the radius of influence parameter, the trend is linear, only the correlation is low.
The linear trend equations obtained in relation to the flow with, the thickness, the transmissibility, the hydraulic conductivity are shown, and the discretionary use of the linear trend equation obtained with the radius of influence.
Acknowledgements
First of all, to God, our father, who has given me a hand to continue on the right path as a person.
To my mother Beatriz Picado, for teaching me the path to success.
To my children Dafned Itziar Tirado Flores, and Víctor Manuel Tirado Flores, I will always be your guide.
To my wife, Lisseth Carolina Blandon Chavarría, who trusts in my successes, thank you for being by my side.
To the American University (UAM) and Faculty of Engineering and Architecture (FIA), for opening the doors of knowledge in this new stage of my life.
To the CASUR sugar mill, for allowing tests to be carried out in their area.
Financing
Own Budget.