Gradiente climatológico en el valle de Loja,

Loja, Ecuador


Climatological gradient in the Loja valley,

Loja province, Ecuador


Victor M. Ponce  
  San Diego State University,
  California, USA

Fernando Oñate-Valdivieso  
  Universidad Técnica
  Particular de Loja, Ecuador


08 November 2014 [08 noviembre 2014]


RESUMEN

La precipitación media anual y la temperatura media anual a lo largo del valle de Loja, Ecuador, se han calculado a partir de datos de siete (7) estaciones climatológicas, seis (6) de ellas operadas por la Universidad Técnica Particular de Loja, y una (1) por el Instituto Nacional de Meteorología e Hidrología. Los resultados muestran un gradiente definido de la precipitación media anual en la dirección Norte-Sur. La precipitación media anual varía de 900 mm hacia el límite norte del valle a 1400 mm cerca del límite sur. La diferencia se atribuye a la elevación más alta del nudo de Cajanuma hacia el sur, en comparación con la del nudo de Guagra-uma hacia el norte. La precipitación anual en el centro del valle es de 900 mm, mientras que la temperatura media anual es de alrededor de 16°C . Se juzga que ambos valores están cerca del óptimo desde el punto de vista del potencial biótico.

ABSTRACT

Mean annual precipitation and mean annual temperature along the Loja valley, Ecuador, have been calculated using data from seven (7) climatological stations, six (6) of them operated by the Universidad Técnica Particular de Loja (Private Technical University of Loja), and one (1) by the Instituto Nacional de Meteorologia e Hidrologia. The results show a definite gradient of mean annual precipitation in the north-south direction. Mean annual precipitation varies from 900 mm toward the northern limit of the valley to 1400 mm near the southern limit. The difference is attributed to the higher elevation of Cajanuma Knot to the south, as compared to that of Guagra-uma Knot to the north. Mean annual precipitation along the valley's center averages 900 mm, while mean annual temperature is around 16°C. Both of these values are judged to be near optimal from the standpoint of biotic potential.


1.  INTRODUCTION

The city of Loja is the capital of Loja province, in Ecuador. The city is located near the center of the Catamayo-Zamora transect, where ecohydroclimatological research is being conducted by the authors (Ponce and Oñate-Valdivieso, 2014). Mean annual precipitation varies between 400 mm in Catamayo, to the west, and 2200 mm near Zamora, to the east. The city of Loja occupies the narrow valley of Loja, between the Guagra-uma knot to the north and the Cajanuma knot to the south (Fig. 1) (Wolf, 1892).

Lateral view of the Loja valley.

Fig. 1   Panoramic view of the valley and city of Loja.

The valley of Loja, oriented from north to south, is divided into two different sections. The northern section is narrow, resembling a canyon. The southern section, properly the valley of Loja, is oval-shaped, with a total length comprising about 9 km and a maximum width of about 6 km (Fig. 2).

Aerial  view of the Loja valley.

Fig. 2   Aerial view of the Loja valley.

The Malacatos river has its headwaters in the Cajanuma Knot (Fig 3), flowing north to meet the Zamora river at Loja proper. Continuing to flow north, the Zamora river flows through the Guagra-uma knot (Fig. 4), after which it meets several tributaries along its course, eventually discharging into the Santiago river in the eastern lowlands of Zamora-Chinchipe province.

The Cajanuma Knot.

Fig. 3   The Cajanuma Knot.

The interandean valley of Loja is small and low, at 2150 m altitud, with the city of Loja occupying almost the entire valley. The lowest point on the road (pass) from Loja through Cajanuma Knot to the south is at 2525 m altitude. The lowest point on the road from Loja to Catamayo to the west is at 2786 m; this pass is next to Villonaco peak, which rises to about 3000 m (Wolf, 1892).

The Zamora river, near Guagra-uma Knot.

Fig. 4   The Zamora river, near Guagra-uma Knot.

This study seeks to calculate climatological gradients in the Loja valley. The study is part of a research program in ecohydroclimatology of the tropics carried out jointly by San Diego State University (San Diego, California, USA) and the Universidad Técnica Particular de Loja (Private Technical University of Loja), Ecuador (UTPL). The logistical support for the field studies was provided by UTPL.


2.  DATA BASE

Data from seven (7) climatological stations in the Loja valley and vicinity were used for this study (Table 1 and Fig. 2). The Universidad Tecnica Particular de Loja operates the first six (6) stations listed in Table 1. In addition, data from the climatological station at La Argelia (in Loja), operated by the Instituto Nacional de Meteorologia e Hidrologia (INAMHI) was used.

Precipitation and temperature data for the years 2011 and 2012 were used to determine the spatial distribution of precipitation and temperature. The spatial distribution of mean annual precipitation was determined by kryging, using ArcGIS®. To determine the isotherms, the mean annual temperature calculated at-a-station (Table 1) was correlated with elevation above mean sea level. The results are shown in Figs. 5 to 8.

Table 1.   Climatological stations used in this study.
Station UTM
(x)
UTM
(y)
Elevation (m) P (2011) (mm) P (2012) (mm) T (2011) (°C) T (2012) (°C)
Colegio Militar 697901 9563240 2033 1058.60 965.20 16.57 16.67
Finca Jipiro Alto 700975 9560679 2218 892.80 874.80 15.25 15.27
UTPL 700135 9559140 2154 874.40 833.22 16.29 16.40
Finca Colegio Técnico 694294 9558872 2377 1241.25 1000.80 14.34 14.38
Ventanas 694716 9555060 2816 1104.00 811.60 11.07 10.97
Villonaco 692138 9559012 2952 1013.60 976.80 10.52 10.36
La Argelia 699718 9553624 2160 1338.60 1096.40 16.2 16.3


Mean annual precipitation in the Loja valley in 2011.

Fig. 5   Mean annual precipitation in the Loja valley in 2011.

Mean annual precipitation in the Loja valley in 2012.

Fig. 6   Mean annual precipitation in the Loja valley in 2012.

Mean annual temperature in the Loja valley in 2011.

Fig. 7   Mean annual temperature in the Loja valley in 2011.

Mean annual temperature in the Loja valley in 2012.

Fig. 8   Mean annual temperature in the Loja valley in 2012.


3.  ANALYSIS

The spatial analysis using ArcGIS® shows a definite gradient of mean annual precipitation in the north-south direction. Given a complete data set of two years (2011 and 2012), mean annual precipitation varies from a low of 900-950 mm toward the northern limit of the valley to a high of 1150-1400 mm near the southern limit. The difference is attributed to the higher elevation of Cajanuma Knot to the south, as compared to that of Guagra-uma Knot to the north (Fig. 2).

Mean annual precipitation averages 900 mm around the center of the valley. Thus, from the standpoint of environmental moisture, the city of Loja is strategically positioned near the middle of the climatic spectrum, with a subhumid climate in the low range (Ponce et al., 2000). Mean annual temperature in the valley's center is around 16°C, considered as a mild climate. These values are close to optimal from the standpoint of biotic potential (Ponce and Aguilar, 2014).


4.  SUMMARY

Mean annual precipitation and mean annual temperature along the Loja valley, Ecuador, have been calculated using data from seven (7) climatological stations, six (6) of them operated by the Universidad Técnica Particular de Loja, and one (1) by the Instituto Nacional de Meteorologia e Hidrologia. The results show a definite gradient of mean annual precipitation in the north-south direction. Mean annual precipitation varies from a low of 900 mm toward the northern limit of the valley to a high of 1400 mm near the southern limit. The difference is attributed to the higher elevation of Cajanuma Knot to the south, as compared to that of Guagra-uma Knot to the north.

Mean annual precipitation along the valley's center averages 900 mm, while mean annual temperature is around 16°C. Both of these values are judged to be near optimal from the standpoint of biotic potential.


REFERENCES

PONCE, V. M., R. P. PANDEY, and S. ERCAN. 2000. Characterization of drought across climatic spectrum. Journal of Hydrologic Engineering, ASCE, Vol. 5, No. 2, April, 222-224.

PONCE, V. M. and R. D. AGUILAR. 2014. The 800-mm isohyet: Health and hope. EWRI Congress: International Perspectives on Water Resources and the Environment, Quito, Ecuador, January 8-10, 2014.

PONCE, V. M., and F. OÑATE-VALDIVIESO. 2014. Ecohydroclimatological research along the Catacocha-Zamora transect, Loja and Zamora-Cinchipe, Ecuador. (In review for possible publication in Tecnología y Ciencias de Agua).

WOLF, T. 1892. Geografía y Geología del Ecuador, publicada por orden del Supremo Gobierno de la República, Leipzig, Germany.


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