According to the United States Census Bureau, the census-designated place (CDP) covers an area of 7.3 square miles (18.8 km2), 98.85% of it land, and 1.15% of it water.

With the approval of the Army Corps of Engineers, a well was dug in 1962 to pipe water from underground springs to create the Lake in the low-lying areas of the Cahuilla Creek watershed and to sustain it.

[4]: 17  The Lake was enlarged to 55 acres (0.22 km2) in 1970, after the property was purchased by a private developer to turn it into a rural residential subdivision.

[4]: 18, 39–41 From early 2016 to late 2019, a swarm of small earthquakes occurred—ranging in magnitude from 0.7 to 4.4 -- the strongest one occurred in August 2018, south of Lake Riverside, just off Cahuilla Road (SR 371).

The remaining more than 22,000 individual seismic events occurred near the western edge of the Cahuilla Reservation stretching 4 km (2.5 mi) northward to just east of the Lake and never generated any significant damage in four years.

The cause of this Cahuilla seismic swarm was traced to a deep natural underground reservoir of fluid, about 8 km (5.0 mi) below the surface, injecting fluid into the base of the fault zone, triggering the swarm of seismic events as it diffused slowly up into the fault zone over the four years.