**3. Materials and methods**

### **3.1 Study area**

Cuautla and Yautepec rivers discharge their waters into the Amacuzac River, main tributary of the Balsas River. Yautepec basin covers an area of 1226 km<sup>2</sup> , which represents 25% of the territory of Morelos State. The total population in 2010 in

**Figure 2.** *Location of the subbasins, meteorological and hydrometric stations of the Yautepec and Cuautla River in the Morelos state.*

these municipalities was 242,197 inhabitants [67]. The region is characterized by the development of new tourist corridors, urban and industrial areas. There are growing problems of pollution and flood risks, which increase the destruction of historical heritage of bridges and dams, with consequences in the incidence of diseases. The Cuautla River subbasin covers an area of approximately 765 km2 . It is located on the slopes of the Popocatépetl volcano to the south of the Morelos State. In the basin, productive processes generate problems of the extraction of soil from the mountains and the soil loss in the upper parts. In addition, a high extraction of water for human and industrial consumption, and consequently, a strong contamination due to the water input of the users of the irrigation districts of the study area (4500), with an area of irrigated land of 10,500 hectares (**Figure 2**) [68, 69].

### **3.2 Methods**

Precipitation variation percentage in the Yautepec and Cuautla river subbasins in the base period (preimpact) and subsequent period (postimpact) was estimated through the precipitation data of the ERIC III weather stations [70]. The weather stations with data from 1924 to 2010 (**Table 1** and **Figure 1**). Eight of them are located in the Yautepec River subbasin and 11 in the Cuautla River subbasin.

The environmental flow analysis in the Yautepec River included three stations: Oaxtepec (upper part), Ticumán (middle part), and Las Estacas (lower part) of the subbasin. In the Cuautla River, the station El Almeal (high part). The comparative study of the monthly average flows of the hydrometric stations of the Yautepec and Cuautla River subbasins, for the preimpact and postimpact periods, was carried out *Water Availability for the Environmental Flow in Two Rivers of Mexico under Climate Change DOI: http://dx.doi.org/10.5772/intechopen.104881*


### **Table 1.**

*Location of the meteorological stations of the Yautepec and Cuautla river basin.*

### **Figure 3.**

*V7 IHA software 33 IHA parameters and their impact on the environment [73].*


**Table 2.**

*Hydrometric stations location river subbasins Yautepec and Cuautla (Morelos state) and years of registers.*

based on the information obtained from the hydrometric stations of CONAGUA (National Water Commission) [71]. Nonparametric graphical and statistical study was analyzed using the software, V7 IHA [72] under the hypothesis that there are no differences between the medians of the preimpact period and the postimpact period (Ho: μ1 = μ2 and Ha: μ1 ≠ μ2). As can be seen below, the 33 IHA parameter (**Figure 3**), V7 IHA is compatible with **Table 1** and Richter's thesis in terms of [65].

The indicators of hydrological alteration (IHA) provided a quantitative approximation of hydrology through the characterization of intra-annual variation of flow by the use. Also, the comparative studies of hydrological regimes before and after system alteration due to human influence or the effects of climate change [74]. Hydrometric stations' location of the Yautepec and Cuautla rivers are given in **Table 2** and **Figure 2**.
