
| Watershed City Population Estimates | ||||||
| CITY Name | 4/1/2000 | 1/1/2001 | 1/1/2002 | 1/1/2003 | 1/1/2004 | 1/1/2005 |
| Anaheim | 328,014 | 331,678 | 335,136 | 337,920 | 343,374 | 345,317 |
| Banning | 23,562 | 23,972 | 24,659 | 25,696 | 27,672 | 27,954 |
| Beaumont | 11,384 | 11,562 | 12,280 | 13,962 | 16,632 | 18,982 |
| Big Bear Lake | 5,438 | 5,592 | 5,745 | 5,905 | 6,064 | 6,148 |
| Brea | 35,410 | 35,917 | 36,910 | 37,961 | 38,998 | 39,584 |
| Buena Park | 77,962 | 78,799 | 79,540 | 80,407 | 80,709 | 81,066 |
| Cerritos | 51,488 | 52,146 | 53,169 | 54,235 | 54,689 | 55,074 |
| Chino | 67,168 | 67,968 | 69,299 | 71,014 | 74,154 | 76,070 |
| Claremont | 33,998 | 34,707 | 35,565 | 36,101 | 36,349 | 36,636 |
| Colton | 47,662 | 48,346 | 49,500 | 50,488 | 51,101 | 51,627 |
| Corona | 124,966 | 129,797 | 134,796 | 138,797 | 144,274 | 144,070 |
| Costa Mesa | 108,724 | 109,765 | 110,872 | 111,668 | 113,118 | 113,440 |
| Cypress | 46,549 | 47,073 | 47,626 | 47,987 | 48,496 | 48,863 |
| Diamond Bar | 56,287 | 57,064 | 58,116 | 58,968 | 59,511 | 59,953 |
| Fontana | 128,928 | 133,577 | 140,332 | 146,577 | 155,749 | 160,015 |
| Fountain Valley | 54,978 | 55,509 | 55,964 | 56,348 | 56,574 | 57,353 |
| Fullerton | 126,003 | 127,861 | 129,496 | 131,659 | 134,314 | 135,672 |
| Garden Grove | 165,196 | 167,310 | 168,877 | 170,151 | 171,204 | 172,042 |
| Grand Terrace | 11,626 | 11,768 | 12,017 | 12,157 | 12,303 | 12,392 |
| Hawaiian Gardens | 14,779 | 14,976 | 15,309 | 15,578 | 15,713 | 15,872 |
| Hemet | 58,812 | 60,052 | 61,869 | 63,017 | 64,889 | 66,455 |
| Highland | 44,625 | 45,140 | 46,202 | 47,714 | 49,553 | 50,860 |
| Huntington Beach | 189,627 | 192,441 | 194,892 | 197,269 | 199,025 | 200,763 |
| Irvine | 143,072 | 148,834 | 157,608 | 165,148 | 171,987 | 180,803 |
| La Habra | 58,974 | 59,978 | 60,786 | 61,273 | 61,512 | 61,771 |
| La Habra Heights | 5,712 | 5,810 | 5,938 | 6,071 | 6,152 | 6,193 |
| La Mirada | 46,783 | 47,349 | 47,956 | 48,925 | 50,156 | 50,477 |
| La Palma | 15,408 | 15,555 | 15,867 | 15,976 | 16,054 | 16,112 |
| Lake Elsinore | 28,930 | 30,045 | 31,250 | 33,469 | 35,989 | 38,045 |
| Lakewood | 79,345 | 80,343 | 81,414 | 82,342 | 83,143 | 83,674 |
| Loma Linda | 19,228 | 19,820 | 20,350 | 20,793 | 21,078 | 21,592 |
| Long Beach | 461,522 | 467,315 | 473,363 | 481,026 | 487,305 | 491,564 |
| Los Alamitos | 11,536 | 11,643 | 11,735 | 11,834 | 11,945 | 12,003 |
| Montclair | 33,049 | 33,558 | 34,145 | 34,494 | 34,942 | 35,530 |
| Moreno Valley | 142,379 | 144,401 | 147,340 | 151,887 | 157,865 | 165,328 |
| Newport Beach | 70,032 | 71,612 | 72,622 | 81,435 | 82,255 | 83,120 |
| Norco | 24,157 | 24,497 | 25,026 | 25,516 | 25,861 | 26,703 |
| Ontario | 158,007 | 160,070 | 163,661 | 166,595 | 168,960 | 170,373 |
| Orange | 128,868 | 131,440 | 133,174 | 134,757 | 136,828 | 137,751 |
| Perris | 42,805 | 43,422 | 43,981 | 44,564 | 45,039 | 45,731 |
| Placentia | 46,488 | |||||