Ring of cenotes geohydrological unit (I)

This geohydrological unit comprises most of the municipios of the former henequen-producing region, including the coastal municipios, Telchac Puerto, Dzidzant´um, and Hunucm´a, and the municipios of Kanas´ın, M´erida, and Um´an, which together with the municipio of Progreso, located in the coastal region, con-stitute the metropolitan region of M´erida.

Table 2.1. Area and population of the socioecological regions of the Yucat´an peninsula.

Population Population density

Code Region State Area (km²) (1990) (persons/km²)

IA Metropolitan Yucat´an

region of M´erida 1,636.32 658,458 402.4

IB Former henequen- Yucat´an

producing region 6,807.20 250,077 36.7

IIA Cattle-producing Yucat´an

region 8,712.39 101,491 11.6

IIB Maize-producing Yucat´an

region 19,451.32 250,833 12.9

IIIA Fruit-producing Yucat´an

region 6,576.01 102,087 15.5

IIIB Hills and valleys Campeche

region 38,239.00 218,344 5.7

IIIC Campeche region Campeche 3,411.00 173,645 51.0 IV Candelaria region Campeche 15,206.00 143,196 9.4

VA Tourist–urban Quintana

region Roo 2,311.00 221,668 95.9

VB Northern block- Quintana

fault basin region Roo 9,227.00 26,633 2.9

VC Southern block- Quintana

fault basin region Roo 39,305.00 244,976 6.2

State of Yucat´an 43,183.24 1,362,940 31.5

State of Campeche 56,856.00 535,185 9.4

State of Quintana Roo 50,843.00 493,277 9.7

Yucat´an peninsula 150,882.20 2,391,402 15.8

Source: INEGI, 1991.

The Yucat´an peninsula has two main types of climate (hot and subhumid, and hot and dry) and 12 subtypes of climate. The ring of cenotes geohydrological unit has the following climate subtypes:

Semiarid, hot (average temperature of the coldest month above 18C) with sum-mer rains and a high percentage of winter rainfall. This climate type is found in both a narrow zone between Sisal and Santa Clara, and the Alacranes reef.

Semiarid, but not as dry as the climate subtype above, with a more marked dry spell in the middle of the summer rainy season. This type of climate is characteristic of the northern part of the state of Yucat´an, between Celest´un and Las Coloradas up to El Remate in the state of Campeche.

Hot, the driest of the subhumid climate type, with summer rains and a sizable dry spell in the middle of the main rainy season. This type of climate character-izes a large zone in the northern and central part of the state of Yucat´an and the northern part of Campeche, the city of M´erida, the Puuc hills, and the Chenes zone in Campeche (Garc´ıa, 1978; Duch, 1988).

This area has generally flat terrain. Landscape slopes increase toward the south, particularly in the Sierrita de Ticul. Geologically, it presents strata from the Quater-nary (Holocene and Pleistocene) and from the Carrillo Puerto Formation (Miocene–

Pliocene) with intermingled materials from the Oligocene limiting, with rocks of the Chumbec Member (Eocene) to the southeast, and with geological materials from the Pist´e Member (Eocene) to the south. For details on the geological materi-als of the peninsula, see Villasuso and Mendez (1997).

The ring of cenotes is an important feature of the hydrogeology of this unit (Vel´azquez, 1986). Mar´ın (1990) hypothesized that the semicircle of cenotes is a high-permeability duct that transports underground water toward the coast.[4]

The main soil types of this region are rendzinas and lithosols. Calcareous regosols are characteristic of the coastal area. The main vegetation type is low (8–15 m) or medium (15–20 m) deciduous forest and low (8–15 m) forest with cactuses and Beaucarnea pliabilis. Savannas and mangroves predominate in the coastal zone.[5]

This geohydrological unit encompasses the metropolitan region of M´erida and the former henequen-producing region.

Metropolitan Region of M´erida (IA)

The city of M´erida changed from being a small town in the middle of the 19th century to being the capital city of one Mexico’s richest states at the beginning of the 20th century. During the early 20th century, M´erida was a booming city. Its expansion originated from economic activities related to henequen production and processing. From such developments, several industrial, commercial, and service activities evolved in the city that have helped it to partly overcome the effects of the henequen crisis.

At the beginning of the henequen boom, the port of Progreso, around 30 km from M´erida, was established for henequen export. Thus, the economy of Progreso was integrated into M´erida’s economic dynamics.

If the Yucat´an peninsula is viewed as a network, the metropolitan region of M´erida is its main node. At the peninsula level, the region generates about 52% of the mining gross domestic product (GDP), 72% of the manufacturing GDP, 48%

of the commercial GDP, and 27% of the services GDP. In 1990, about 50% of the

population of the state of Yucat´an and 33% of that of the Yucat´an peninsula were concentrated in this region (INEGI, 1991, 1996).

Due to the effects of the henequen crisis, the close proximity of M´erida, and that city’s sprawl, the municipios of Kanas´ın and Um´an and their main human set-tlements are becoming increasingly integrated with the city of M´erida. The decline of the agricultural sector has resulted in a recent increase in rural–urban migration, which has contributed to M´erida’s population growth.

Geomorphologically and hydrologically, three municipios of this region (M´erida, Kanas´ın, and Um´an) are located in the semicircle of cenotes, and one (Progreso) is located in the coastal zone.

Water use is distributed approximately as follows: agriculture, 42%; services, 19%; public entities, 15%; industry, 15%; and livestock production, 5%; with other uses accounting for the remainder. Most wells are located in the municipio of M´erida (65%) and in Um´an (25%). Kanas´ın and Progreso each have about 5% of the wells in the region.[6] Management of wastewater is a very serious health issue, particularly, but not exclusively, in urban centers. This situation is partly illustrated by results from Cabrera et al. (n.d.), who found nitrates in underground water in the city of M´erida at levels between 10.3 and 39.6 mg/l, higher than the allowed threshold value of 5 mg/l.

Former Henequen-producing Region (IB)

The invention and widespread use of agricultural machinery in the United States during the second half of the 19th century increased the demand for henequen (or sisal) fiber, which was used to bind agricultural products. The area where henequen was cultivated expanded up to a radius of approximately 80 km from M´erida and became known as the henequen-producing region.

In 1937, agrarian reform led to changes in the structure of henequen produc-tion and a dismantling of its main organizaproduc-tional unit, the hacienda. Thereafter, the state intervened, taking over henequen production.[7] The government’s inter-vention deepened in the following decades as it acquired henequen manufacturing plants, thereby exercising total control over henequen agricultural, industrial, and commercial activities. Despite this governmental control, vertical integration be-tween fiber production and its processing/marketing was not established. Henequen production was controlled by development banks, whereas the other activities were directed by the Ministry of Industry and Commerce.[8] As a result, the manage-ment of henequen production and its marketing were inefficiently carried out, and the industry was unable to respond properly to the challenges of the international market. Changes in the external environment included more efficient production systems in competing countries, an increasing share of the world market for natural fiber by sisal-producing countries such as Brazil and Tanzania, competition from

synthetic fibers, and the emergence of new technologies requiring less natural fiber.

Henequen production peaked in the 1950s and started to decline significantly after 1960. In 1992, after more than 50 years of intervention, the state pulled out of henequen-related activities.

The economic problems originating from the henequen production crisis have been partly counterbalanced by a series of development programs. Poultry and pig production programs have been promoted in the western and southern parts of this region. In some municipios, horticultural production, particularly citrus production, has been encouraged.[9] Maize production for subsistence has been promoted, primarily in remote municipios. At the same time, employment has increased in the construction and service sectors of M´erida and, more recently, in the maquiladora sector.

Generally, however, the henequen production crisis led to an increase in unem-ployment, a decrease in income, and a deterioration of the population’s standard of living, resulting in important migratory flows to M´erida and to the tourist regions of Quintana Roo. Henequen production continues to be an important activity in this region; however, it is no longer the main source of income for the region’s inhabitants.

Water is chiefly used in crop production (84%), livestock production (12%), and in public services (4%). The highest well concentration is found in the following municipios: Samahil, 15%; Hunucma, 13%; Kinchil, 6%; and Abala, 6%.