Guejito Hydrology and Guejito Creek
The Guejito Ranch contains some interesting hydrological features that are mapped below using GIS. The primary drainage is Guejito Creek which has its headwaters on Pine mountain in the northern highlands of the ranch and which terminates in the San Dieguito River just outside the southern tip of the ranch. The secondary 17,800 acre Guejito Creek Watershed
drains into the primary San Dieguito River Watershed which empties into the ocean. It is remarkable that the watershed of Guejito Creek is almost entirely within the boundaries of Guejito ranch (see map below) and I now of no other property that so captures a secondary watershed. USGS Guejito Creek Stream Gage here.
The available water supply in this area was studied in 1902 and again in 1974. The 1902 report came about as the Vineyard Ranch was under consideration as an Indian reservation and concluded that the ranch was an inferior sites largely because there was "not evidence that any reasonable amount' of water can be developed" In 1974 The State Parks 1974 feasibility study stated "the lack of an ample water supply precludes such use" as "residential development".
As the minor tributaries of the Creek gather off of Pine Mountain the converge in the more level northern pasture above a narrow gap in the hills. All of the watershed above the narrows must exit through this restricted passage. Apparently this restriction and the gradual terrain has created a substantial opportunity for wetlands to form above the narrows. Cattle grazing makes it difficult to estimate the potential wetlands available but large areas are worthy of investigation.
GIS map showing hydrologic features of interest around Rancho Guejito
After the gathered creek passes through the narrows it flows through the remainder of the northern pasture and enters oak woodlands. There among the oak studded southern hills it is joined by tributaries from the slightly higher southern pasture and another large wetland of a more wooded nature is clearly evident.
Passing out of this area the creek gains momentum as it heads down the mountainside into San Pasqual. Old newspaper reports state that there is a waterfall in this area and the very steep slopes shown on map results confirm this potential although it may be more cascading than outright falls.
Older maps show a mark for Bear Spring in a valley below Pine Mountain which by acounts is a consistent producer.
I believe some evidence suggests that geology underlying the loamy soils of the grasslands may restrict deeper drainage and retain moisture within the grassland areas. This might in part account for the formation of the Guejito's natural grassland areas which are above steep slopes on plateaus or piedmonts rather than in valley bottoms where one might usually expect such soils. One can see the rivulets in pasture areas that can be traced as the very beginnings of several area canyons and it is somewhat mysterious why the meadows of the Guejito have not geologically eroded away leaving canyons like those so familiar to North County.