The hydromorphological quality of the basin of Mexico: A proposal of its indicator value of the ecological state in the riparian ecosystem

Resumen

The characterization of hydromorphological quality is the evaluation of the physical structure and the flow regime associated with fluvial ecosystems. Its value indicates the state of ecosystem conservation, as well as the anthropogenic pressures that disturb it. The present study proposes an hydromorphological quality (HYQI) index that aims to establish reference conditions in the preserved rivers and springs in the Basin of Mexico, through: (i) the basin quality associated with the riparian zone’s state, including the vegetation’s naturalness, level of erosion, and land use in 13 sub-basins (63 sites); (ii) hydrology, related to natural or disturbance conditions in the channel; (iii) anthropogenic alterations in the riparian zone, and (iv) the characterization of the trophic level. The final evaluation is divided into five classes: high (> 100), good (76-99), moderate (51-75), bad (26-50), and poor (< 25). The HQYI evaluation showed that 44 sites have a high rating (120 to 100 points), where potential reference conditions for the Mexico Basin can be recognized. The remaining 19 sites have good to poor quality conditions. The vegetation cover was represented by 70% of native species in one of three types of forest: Pinus, Abies, and mixed forest dominated by Quercus. Modifications in the canal structure, extraction and retention of water, and introduced plant species were the causes that confirmed the moderate quality value in the middle and lower portions. The HQYI value was found to be significantly correlated with nutrient water enrichments with soluble reactive phosphorus and dissolved inorganic nitrogen. Therefore, this index is recommended for monitoring the Basin of Mexico and registering multiple environmental stressors.