Groundwater
Because the climate is dry, groundwater is very important in Central Asia for drinking water, irrigation and watering livestock. In mountain areas the source of groundwater is precipitation, which passes through rock cracks and karst passages and emerges as springs that join rivers. On the plains groundwater forms artesian basins, whose source is water seeping from river channels and mountain slopes. In the Kyzylkum and Karakum artesian wells up to 200–250 m deep have been dug for livestock. Water lying deep in cracks is often hot and rich in minerals; this is called thermal and mineral water. Sanatoriums and resorts such as Chimion, Chartak, Polvontosh, Jayronkhona (Surkhandarya) and Obigarm (Tajikistan) operate on it. In ancient times kariz (underground channels) and sardoba (covered cisterns) were built at the foot of mountains to collect water.
“Well model”: layer sand, gravel and clay in a transparent container and pour water over it: watch which layer lets water pass quickly and where it collects. Do this under adult supervision.