Aquatic systems and water security in the Metropolitan Valley of Mexico City
In megacities water quantity and quality are threatened by complex and interrelated processes caused by population growth, land use change, unsustainable agricultural practices, deforestation, erosion, destruction of ecosystems, lack of planning, laissez-faire policies, unsustainable water management, political conflicts, and increasingly also by the impacts of climate change. In the Metropolitan Valley of Mexico City (MVMC) located in the high plateau of Mexico City and on former lakes, the dry out policies during the last 300 years have been counterproductive, causing scarcity, pollution, health and environmental problems, subsidence and water conflicts, particularly affecting social vulnerable people. Megacities require an integrated management of water and aquatic systems — integral water resource management, rainwater harvesting, maintenance and replacement of infrastructure, restoration of ecosystems and urban planning. This implies investments and a water culture including a transparent administration and peaceful negotiation of conflicts regarding concessions, access, and reuse of water allocation. Socio-political and environmental processes are complex; besides technical factors and ecosystem recovery, socio-cultural changes must transform human settlements and power structures.
The Growth of Water Demand in Mexico City and the Over-exploitation of its Aquifers
Mexico City – with a population of more than 20 million people – is confronting one of the most serious short-term water resource problems in the world. This is due to an inability to supply water to several of its zones, as well as to a reduction in supply during drought periods. The medium- and long-term problem is severe because supply, which is inelastic, cannot meet a growing demand. The impressive urban growth of Mexico City has encouraged a water policy that has over-exploited groundwater bodies within its boundaries; since the local supply is insufficient, the city now extracts ground and surface water from adjacent basins. These basins include the Lerma and Cutzamala Basins. Currently, the risk is that this complicated and costly system will collapse, with grave environmental, economic, political, and social consequences.
Assessment of Ground Regeneration around Borehole Heat Exchangers between Heating Seasons in Cold Climates: A Case Study in Bialystok (NE, Poland)
Based on the experimental studies, the process of ground regeneration around the borehole loaded with brine-water heat pumps working exclusively for heating purposes in the period of four consecutive heating seasons in a cold climate was presented. The research was conducted in north-eastern Poland. The aim of the work is to verify the phenomenon of thermal ground regeneration in the period between heating seasons on the basis of the recorded data and to check whether the ground is able to regenerate itself and at what rate. It was noticed that the ground does not fully regenerate, especially during heating seasons with lower temperatures. In the analyzed period, from 22 September 2016 to 12 October 2020, the ground probably cooled irreversibly by 1.5 °C. In order to illustrate and evaluate the speed of changes in the ground, the one’s profile with an undisturbed temperature field was presented for each month of the year. The presented results can be a very important source of information for the analysis of geothermal conditions occurring in the ground. They can be used to verify mathematical models and conduct long-term simulations that allow us to see the complexity of the processes taking place in the ground.