Excavated pond. or "dug pond". They are harder to build because of earth removal. They are more resistant to collapse by erosion - no dam.
underground aquifers
The weakest kind of erosion is probably sheet erosion, which is a gradual removal of thin layers of soil over a large area due to rainfall and surface runoff.
Freshwater marshes are wetlands that contain water with low salt content, typically derived from rainfall, surface runoff, and groundwater. These marshes support a variety of plant and animal species adapted to freshwater conditions and play important roles in flood control, water purification, and habitat provision.
groundwater
A shield volcano - a huge, flat shape, kind of like a giant contact lens made of rock and filled with magma, pressed against the earth's surface
Groundwater pollution.
its clay
Groundwater, freshwater, and melted water
Soil erosion.
runoff im in the sixth grade
In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many parts of the world, in some cases contributing high fractions of the annual runoff in a watershed. Predicting snowmelt runoff from a drainage basin may be a part of designing water control projects. Rapid snowmelt can cause flooding. If the snowmelt is then frozen, very dangerous conditions and accidents can occur, introducing the need for salt to melt the ice
Cenotes would be very important sources of groundwater in arid or semi-arid landscapes where surface water is scarce. Regions with porous limestone bedrock, such as the Yucatan Peninsula in Mexico, are particularly reliant on cenotes for freshwater due to the lack of surface rivers and lakes.