Questions: How do New Mexican water sources become brackish? - Seawater infiltration from long distances - Salt infiltration from streams - Rainwater intrusion - Evaporation concentration of salts

The answer is the fourth one: evaporation concentration of salts.

Explanation for each option:

1. Seawater infiltration from long distances: This is unlikely because New Mexico is a landlocked state, far from any ocean. Seawater infiltration over such long distances is not a plausible explanation for brackish water in this region.

2. Salt infiltration from streams: While streams can carry salts, this is not the primary mechanism by which water sources in New Mexico become brackish. Streams in New Mexico are generally not saline enough to cause significant brackish conditions.

3. Rainwater intrusion: Rainwater is typically fresh and would dilute salts rather than concentrate them. Therefore, rainwater intrusion would not make water sources brackish.

4. Evaporation concentration of salts: This is the most likely explanation. In arid regions like New Mexico, high evaporation rates can concentrate salts in water sources. As water evaporates, the salts are left behind, increasing the salinity and making the water brackish.

Summary: New Mexican water sources become brackish primarily due to the evaporation concentration of salts.