possesses a significant quantity of water resources; its average total runoff is 43,500 m3 per

inhabitant a year, four times greater than the world average of 10800 m3 per inhabitant

(Machado, dos Santos, Alves, & Quindeler, 2019). Water quality is at risk due to human

activities near water sources. These activities are usually related to urban areas, mining

areas, oil exploitation, and agriculture. These activities generate pollutant discharges with

high concentrations of organic matter, nitrogen, phosphorus, heavy metals, and

hydrocarbons (Ustaoğlu, Tepe, & Taş, 2020). Agricultural activity is extensive in the

province of Chimborazo due to favorable climatic and geographical conditions (Moreano-

Logroño & Mancheno-Herrera, 2020). In the last ten years, the Guano River has been used

mainly in agricultural activities; in its course, it receives sanitary, agricultural, and industrial

& Liang, 2020; Uddin, Nash, & Olbert, 2021; Villa-Achupallas, Rosado, Aguilar, & Galindo-

Riaño, 2018). These indexes allow researchers to gather information on trends and identify

river disturbances sources. Additionally, these indexes are necessary to study the

characteristics of water resources and their quality to ensure the balance between human

activities and the water ecosystem (Rivera, Encina, Muñoz-Pedreros, & Mejias, 2004). The

US National Sanitation Foundation - water quality index (WQI-NSF) is used worldwide for

this type of study. This method referred to here as Ramirez’s approach, is based on

characteristics of North American rivers, which relate physical-chemical variables to

average weights assigned to each for evaluating the specific pollution type (Gradilla-

River, using a variation of the WQI-Dinius that includes variables such as the average slope

and the river’s flow. In addition, this work compares the results obtained with this variant

in the index with WQI-NSF and WQI-Dinius.

The Guano River basin (Figure 1) is located in the Ecuadorian highland between

Tungurahua and Chimborazo; the river is the product of the thaws from Chimborazo’s

volcano and the runoffs generated in the Igualata moorland. The river’s source is

downstream of Andaluza, in the area of Llío, where the Agags and Puluchaca streams merge

at 3090 masl. The Guano River flows from northwest to southeast and runs into the Chambo

basin areas. In addition, the rate of population area corresponds mainly to the town of

Guano, which sits on the banks of the river and is the one that shows the most significant

interference in its quality. To determine the sampling points, vegetation and land use

information (Mendoza et al., 2021) were analyzed (Table 1). The river was traversed from

the upper part to the river mouth, corroborating what was identified in the characteristics

of land use and vegetation data.

and the human activities that affect the river’s environmental conditions; thus, 29

with the peak of the bottle in the direction of the current until filled the bottle free of bubbles

Laboratory analysis for water was performed according to the Standard Methods for the

Examination of Water and Wastewater (23rd ed.) (Rice et al., 2017) as described below:

closed immediately and shaken vigorously for 20-30 s. After this, the sample should be

and ammonium hydroxide) to give a pH of 10.0 to 10.1. Next, 1 to 2 drops of indicator

solution or an appropriate amount of dry-powder indicator formulation (Eriochrome Black

stirring, until the last reddish tinge disappears. The last few drops should be added at 3 to

5 s intervals. At the endpoint, the solution typically turns blue.

The Titration Method 2320 CB for Alkalinity (mgCaCO3/L). In this method, 25 mL of sample

1 to 2 drops indicator solution (Methyl Orange) are added and titrated with a standard 0.1

N sulfuric acid solution. The reagent should be added slowly, under continuous stirring,

until the sample color changes to purple.

Biochemical Oxygen Demand (BOD) 5210 B. 5-Day BOD modified to VELP BOD EVO

determines the BOD5.

Chemical Oxygen Demand (COD) 5220 D, Closed Reflux, Colorimetric Method. One used

HACH DR 5000 spectrophotometer 5000 of Loveland, Colorado, United States. Samples

were gently agitated for 1 min and held in a vial reagent HACH LR (range 3-150 mg COD/L)

at an angle of 45º. A clean pipet was utilized for dispensing 2.00 mL of sample to the vial.

The same procedure was used for another vial filled with deionized water and utilized as

the blank. After closing the vial it should be held by the cap, over a sink. The content of the

vial can be mixed by inverting the vial gently several times. Next, vials are placed in A

preheated DRB200 reactor for 2 h at 120 ºC. After turning off the heat, vials should cool in

the reactor for 20 min to 120 ºC or less and then cool to room temperature in a tube rack.

Membrane filter technique for members of the coliform group 9222 modified to Petrifilm

The flow was obtained with the float method, this is based on the speed-area principle,

where (n) cross-sectional areas (depth and width) were measured, and the velocity was

obtained from the time the float takes to travel a distance (5m). The Manning coefficient

corrects the flow (Davids et al., 2019). Flow information of the different sampling points was

obtained according to equation (1).

From the heights of the contour lines, the tool-created TIN is used to develop the digital

terrain elevation model (DEM). Owing to the transform tool of TIN, the elevation raster of

the study area is generated. From this raster, the Spatial Analysis slope tool is used to

spatially determine the Slope (Sc) in the basin. This is done in the ArcGis 10.1 software

(Mendoza et al., 2021).

In this study, the river course was divided into transects according to the natural

conditions and the human activities present, leaving five monitoring points for studying the

water quality; these points were chosen based on the pressure on different transects, as

shown in table 2. The methodology of the water quality indices applied at the sampling

from 0 to 100 (Akhtar et al., 2021; Gupta & Gupta, 2021; Mukate, Wagh, Panaskar, Jacobs, &

where Wi is the weighting coefficient for parameter i, I is the index for each parameter, and

The second methodology described by Dinius determines the water quality of the sample

according to the degree of water pollution. Thus, it will have a quality index close to 0 for

utterly contaminated water. The index will be 100 for water with excellent conditions

(Hoseinzadeh, Khorsandi, Wei, & Alipour, 2015; Mukate et al., 2019; Zotou, Tsihrintzis, &

Gikas, 2019, 2020). Subsequently, this index indicates that a correction should be made to

The numerical evaluation of the WQI-Dinius is obtained from the geometric mean (Equation

where Wi are the specific weights assigned to each parameter (i), and weighed between 0

and 1, so the sum is equal to 1. Qi is the quality of the parameter (i), which depends on its

concentration, and is rated from 0 to 100. PI represents the multiplication of the variables Q

elevated to power W.

To contemplate the geomorphology and flow of the Guano River in the calculation of water

quality, the WQI-Dinius was modified; therefore three steps were considered: (i) selecting

the parameters, (ii) determining the sub-indexes, and (iii) determining the index by

aggregation (Mukate et al., 2019; Samboni et al., 2007). For this purpose, the selection of

geomorphology characteristics: mean average of the Slope, Slope of the river course in the

area under study, and flow. To apply the WQI-Dinius Modified, equation (4) was used. The

I values were obtained from table 4, and the geomorphological characteristics (I) are equal

to 1. The importance of W (WQI- Dinius Modified) for this method are described in table 5.