A topographical analysis of the area under study was carried out with topographic precision equipment, which was subsequently revised, through use of Digital Elevation Models DEM taken from the US Geological Survey in the United States of America [10]. There is evidence, in aerial photographs and IGAC cartography, that, in some periods, water bodies appear perfectly delimited, and in others, they disappear, which describes the seasonality of the wetland.

Toponymy refers to the study of proper names used by locals. In this case, because there is new urban development, very few people have knowledge of the area. A number of seniors, however, do have knowledge of the Yaporogos Lagoon. Another reference to this ignorance was found on the IGAC topographic maps from 2005, which use a 1:25,000 scale. Therein, no reference was made to the Yaporogos Lagoon, thus this point was inconclusive, given the scale of the wetland.

The topography of the area was naturally lower than the surrounding areas, a fact which was validated in the field by topographic precision equipment and by means of DEM analysis, which used the topographic index [28]. This facilitates the accumulation of subsurface water during wet seasons. It also showed the existence of natural drainage, which leads surface runoff water to the area in which the body of water that was previously modified was relocated. Such drainage has been used by the owners of the nearby lots in both the past and present to drain water. It has been rerouted, in accordance with the needs of the neighboring buildings. However, it still fulfills its hydrological purpose, which is to drain water towards the Magdalena River, located downstream.

According to the plan for the management of the Magdalena River basin - eastern slope of the Cundinamarca department [23], the study area is characterized by a warm, semiarid climate, according to the Caldas-Lang classification, with a bimodal rainfall regime, associated with the Inter-Tropical Confluence Zone, ITCZ [29], where the first wet season is the most intense, and which occurs from the end of April to June. The second occurs from September to November. Monthly minimums occur in January and July, amounting to approximately 45 mm of monthly rain, with an average annual rainfall of approximately 1,400 mm [23].

The average temperature in the region is 28 ° C, with minimal variations throughout the year. The difference in thermal gradient between the warmest and coldest months is 3 ° C. The relative humidity averages 65% monthly, and behaves analogously to precipitation, with maximums in rainy seasons. Meanwhile, the potential of evapotranspiration presents a tendency opposite the rains, which generates a water deficit in the summer seasons.

The region has dry tropical forest type vegetation, but in the study area, the bush and shrub areas predominate. Said shrubby vegetation blooms during rainy season and loses its foliage during the dry period, a behavior which responds to climatic variability and the strong anthropic intervention of livestock and agriculture activities [23].

Old Agustín Codazzi Geographical Institute (IGAC) images and those of Google Earth permit the location of the water mirror, called Yaporogos Lagoon by the community. There, additionally, there is a channel flowing SW-NE and an outcropped water mirror. In order to carry out this analysis, images were taken from Google Earth [25], the first of which was captured on December 31, 1969, as shown in Fig. 2. Although its resolution is low, when focused on the municipality, one may ovserve that, at the time, the study area at the Yaporogos Lagoon was not surrounded by buildings. An aerial photograph of the year 2012, which is presented in Fig. 3, shows the area of interest in greater detail, and indicates a significant urban change, with a considerable increase in new construction. In the 2012 image, abundant vegetation is observed, while in Fig. 4, from 2015, the vegetation is shown to be considerably reduced by burning in the area, followed by the sprouting of pastures and ground vegetation, which is observed in the present, as indicated in Fig. 5 [25].

Figure 2 Source: Adaprted from Google Earth.

Figure 3 Source: Adaprted from Google Earth.

Figure 4 Source: Adaprted from Google Earth.

Figure 5 Source: Adaprted from Google Earth

The Magdalena River valley, at the height of the Tolima and Cundinamarca departments, is characterized by limestone and sandstone strata. Additionally, multiple eruptions of the Machín and Tolima volcanoes have deposited pyroclastic flows on the banks of the Magdalena River [23].

In the study zone, sedimentary rocks from the Honda group (Ngh), as well as “Abanico de Espinal” (Qae) discordant volcanoclastic deposits may be identified, as documented in the Colombian geological map 1:100.000 from the IGAC, created in 2013. The Honda group is comprised of typical, greenish gray sandstone that was established in the San Antonio Mountain Range, east of the town of Honda [30]. In the study area, the Honda group emerges southwest of Girardot in the Flandes area.

The range of Espinal (Qae), originated with the contribution of the Cerro Machín volcano, with a high volcanic content and finer material from the Quaternary Age. This fan, in the flat area between Flandes and Espinal, is used for agriculture, with sporadic levels of gravel, high porosity, and hydraulic conductivity. These deposits, with their high bearing capacities, are also exploited as building materials [31].

Geomorphologically, it is identified as a discharge zone for the Central Mountain Range, a superficial accumulation that depends on the physical properties of said deposits and lithological outcropping units. In the study area, the unit called the Honda group was identified, whose lithological composition favors accumulation. Thus, it may be identified as a potential aquifer area. Additionally, its undulated surface favors the accumulation of water bodies dependent on lithology and climate. These processes led to the formation of fluvial system geoforms. For previous geoforms, the composition of the sediments varies significantly, aspects which may be analyzed for the reconstruction of accumulation environments.

The chemical composition of continental water varies widely, mainly due to the lithological variability of the basin or lake, climate, vegetation, and environmental factors. Anthropogenic factors are also important because they directly affect soil erosion, agricultural-livestock activities, irrigation, as well as the negative impact in the area destined for waste dumping and urbanization. All of these tend toward the accumulation and concentration of compounds that, in their organic degradation process, mineral or ionic substances permeate the Magdalena River [32].

Algae are commonly used in the biological characterization of the ecosystem, determination of the healthiness of a water resource, and its subsequent use for different applications [33]. Diversity, the combination of morphological, physiological, and reproductive characteristics make algae important diagnostic organisms, suitable for use and application in ecosystem analysis and evolution [34].

Paleoecological, paleolimnological, paleoenvironmental, and paleoclimatic research use diatoms as indicators which provide valuable information, due to the sensitivity of this group of algae to environmental changes, including valve preservation in lake sediments [35]. Additionally, paleolimnological conditions reflect local environmental conditions, specifically precipitation and evaporation, two of the most important climatic factors [36].

Geophysical methods are based on the measurement of certain physical properties of the materials contained in the earth's crust: density, magnetic field, electrical conductivity, speed of transmission of elastic waves, etc. The interpretation of these measurements, based on the contrasts between, and anomalies observed, allow for preparation of models with the characteristics of the subsoil and its spatial distribution. Surface electrical studies represent a method of analyzing geomaterials in terms of their electrical properties. Of these, resistivity has been related to petrophysical parameters such as porosity and the degree of saturation. The acquisition of field data may be carried out with electrode configurations, which can vary in their arrangement, and that strictly depend on the object upon which the scan is performed. A common configuration in these electrical methods is the Vertical Electrical Probe (VEP), as it is possible to produce one-dimensional models that correspond to discrete points on the surface [27].

In this study, electrical surface studies were carried out, using a method of geomaterial analysis, in terms of its electrical properties, which are subsequently compared to petrophysical parameters, such as porosity and degree of saturation. The configuration employed was Vertical Electrical Sounding (VES), whereby geomaterial resistivity values were found in the area of interest from 5Ωm to 34Ωm. This variation in resistivity values is due to the humidity and salts present. The resistivity is characteristic of fine geomaterials (clays - limes) that, in saturated conditions, present resistivity values ranging between 5 Ωm and 20Ωm, and in unsaturated conditions, between 20Ωm and 40Ωm. This, in turn, depends on the concentration of salt present in the water which saturates the geomaterial.

A complete study requires a biological analysis, in order to establish the existence of certain ecosystemic relationships that can define the existence of a wetland. They usually make use of certain ecological attributes, such as wealth, abundance, and diversity, among others, of the biological communities. For the present study, the community of phytoplankton algae in water and soil diatoms were used, and whose determinations were made by the taxonomic gender category, which is based on the works and taxonomic guides of [37-43] and the http://www.algaebase.org/ global database.

The purpose of the biological tests was initially to extract a nucleus from the deepest zone, where a depression in the ground had been detected, in order to establish whether there was evolution in the aquatic ecosystem, through the use of diatoms (Bacillariphyta), via the previously described lithological profile. However, when the area studied was visited, it was found to be flooded, and so a phytoplankton sample was collected, in order to glimpse the water quality of the flooded area by way of these organisms. Twenty-one morphotypes from 15 families, 11 orders, six classes, and five phytoplankton divisions were found. The Bacillariophyta division (diatoms) contributed 29% of the morphotype total (6). Additionally, five (24%) Chlorophyta, and four (19%) Charophyta morphotypes were observed (the last two are green algae), Cyanobacteria contributed four morphotypes (19%), and the Euglenophyta division represented 10% with two morphotypes.

Diatoms (Bacillariophyceae) are unicellular, free-living microscopic algae, although they also form colonies surrounded by mucilage and filamentous individuals [44]. They are observed in all types of habitats, where the light, temperature and chemical conditions are favorable for their growth, and are distributed in all latitudes and longitudes in the world. Thus, they are present in rivers, estuaries, lakes, and marine environments located in various substrates, as well as in humid, cold, and hot springs [45]. The fossil record indicates that diatoms were already a specialized group in the early Cretaceous period [46]. In the Yaporogos Lagoon, it was observed that, although diatoms provided the greatest number of taxa, they were not predominant.

In the phytoplankton sample (extracted from the water) it was found that the taxa with the most predominance was cyanobacteria, Anabaena genus. Species in this genus are planktonic, and sometimes they form water flowers (mainly of the Dolichospermum subgroup) or mats that cover different substrates, aquatic plants, submerged forests, stones, etc. Several species grow benthic or in soils, and several are known saline (brackish) biotopes. Many species have limited geographical distribution areas, but the genus is extensive and common. Some of these form dense superficial blooms, and others register as toxic [39,47].

As for the soil samples, the Hantzschia aff. Amphioxys, Navicula aff. mutica, Sellaphora sp. and Fragilaria sp diatoms were present. On the one hand Hantzschia amphioxys is a cosmopolitan species that is favored in periodically dry habitats, including soils and cracks in rocks, which extends to a wide variety of rivers, and probably washed away by soils. It is also very characteristic of temporary aquatic habitats [43]. On the other hand, Navicula mutica is also a species distributed throughout the world, and is quite common in brackish conditions and in waters prone to desiccation [43]. The ecological characteristics that describe these two species explain their presence in the nuclei far from the flooded area.

While the Fragilaria sp. and Sellaphora genera, with affinity to the pupula species, are typical of wetlands, as is Fragilaria sp. It is abundant in lake plankton, is a taxon that is considered to have been introduced by human activities, and Sellaphora pupula is a species that is found in a wide spectrum of waters rich in electrolytes, with some populations that are in heavily polluted conditions. These situations explain the reasons that these two species were only recorded within the lithological sample extracted from the water mirror, and likewise sustain the conclusion of the liquid sample reading, as it indicates the degree of contamination to which this body of water is exposed.