The county finds itself in the middle of the decennial process called redistricting.
What that means is that each county supervisor is elected from and represents a given area of the county, with each one of those areas having an equal amount of people residing in it or as nearly equal in population as humanly possible.
The reason for the equal number of residents boils down to our republican form of government; that is, we do not rule directly — we elect others to govern for us. Our form of government is also called representational because we elect others — Assembly members, senators, presidents, supervisors, Imperial Irrigation District board members and so forth — to do what they think is in our best interests.
To develop those new boundaries for supervisorial districts every 10 years, the U.S. Constitution requires an "actual enumeration" of the "whole number of persons in each state." To carry out that mandate, the federal government takes a census to determine the actual number, not an estimate.