The water added back into the cooling tower recirculating water stream to replace water lost to evaporation, blowdown, or other mechanisms of water loss.
ADWR Dictionary

ADWR Dictionary
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Make-up water
Managed underground storage facility
A facility designed and managed to utilize the natural channel of a stream to store water underground through artificial and controlled releases of water other than surface water naturally present in the stream. Surface water flowing in its natural channel is not a managed underground storage facility.
Maximum Annual Groundwater Allotment
Maximum amount of groundwater that may be used per year for the irrigation of each irrigation acre in the farm that is calculated pursuant to A.R.S. § 45-465.
Maximum contaminant level
A primary maximum contaminant level (MCL) represents a drinking water standard set by the Safe Drinking Water Act and enforced by the EPA. An MCL reflects a national primary drinking water regulation in the form of an enforceable numeric drinking water standard representing the maximum permissible level of a constituent in a public water system. A secondary maximum contaminant level (SMCL) represents a non-enforceable numeric standard for the aesthetic quality of drinking water, such as taste, odor, or color. Waters with contaminants above a SMCL are not typically expected to cause health problems.
Maximum storage capacity
Total storage space in a reservoir below the maximum attainable water surface elevation, including any surcharge storage.
Metamorphic rock
A rock that is the product of heat, pressure, and chemical activity so that some or all of its minerals are re-crystallized and may show preferred orientation.
Mill circuit
The flow of water used in the process of crushing ore, recovering copper at the mill concentrator, and transporting and disposing of tailings, and includes recovery of water at the tailings impoundments for reuse in the mill concentrator.
Mill Concentrator
The structure at open-pit metal mines within which metallic ore is crushed and the flotation process is used to remove minerals.
Monitor well
A well that is designed and drilled for the purpose of monitoring water quality within a specific depth interval. A.A.C. R12-15-801(1).
Multi-family housing unit
A mobile home in a mobile home park and any permanent housing unit having one or more common walls with another housing unit located in a multifamily residential structure, and includes a unit in a duplex, triplex, fourplex, condominium development, town home development, or apartment complex.
Municipal demand
All non-agricultural uses of water supplied by a city, town, private water company, irrigation district, domestic water improvement district, water cooperative or private domestic well.
Municipal Distribution System
A system of pipes, canals or other works within a municipal provider’s service area which are owned and operated by the provider to collect, store, treat or deliver water for non-irrigation use.
Municipal provider
A city, town, private water company or irrigation district that supplies water for municipal use.