Water Sources
Fresh water is an essential resource for humans. Localized in its availability in the arid or semi-arid climate of most of San Diego County, and burdensome to transport in quantity, water probably exerted a significant influence on prehistoric settlement patterns.
Water sources were not fixed elements throughout the prehistory of the region. Climate varied, rivers shifted their courses, tectonic activity probably opened and closed springs, and human intervention, especially burning, probably altered runoff patterns. Subsequent changes during the historic period have been even more drastic. Reconstructions of prehistoric hydrological conditions can help in interpreting the archaeological record, and, in turn, archaeology may play a role in reconstructing paleoenvironmental conditions.
Changes through time in the adjustments of settlement patterns to water resources were probably the result of cultural changes as well as paleoenvironmental ones. Increases or decreases in community size altered the water requirements at habitation sites. Prehistoric changes in regional population density may have altered the extent to which use was made of locations with less-than-optimal water resources. The availability of ceramic vessels as conventient water containers may have made it more practical to conduct various activities farther from water sources; however, ceramic pots may also have encouraged greater use of boiling as a cooking technique and therefore greater reliance on water.
The majority of the water sources in San Diego County are highly seasonal in their availability. Seasonality of site occupation has usually been interpreted as governed by the exploitation of particular food resources or by climate, but seasonal water availability may have been an equally important determinant.
The importance of water availability must have varied for different site functional types. In particular, the leaching method of removing tannin from acorns would seem to have mandated that water sources be close at hand at acorn processing sites.
Several studies in the region have examined the correlations between site locations and water sources:
- John R. Cook and Scott G. Fulmer (1980) analyzed the hydrological contexts of sites and of survey sample areas lacking sites in the BLM’s McCain Valley Study Area, along the eastern slopes of the Peninsular Range. The McCain study considered the distances to springs and to streams of various ranks (Rank I being an initial drainage, Rank II a drainage below the confluence of two Rank I streams, and so on). Some clustering of sites, particularly habitation sites, near modern water sources was found.
- For Mount Laguna, William R. Graham (1981) analyzed the distances of sites of various types from different types of water sources, including permanent springs, good streams, fair streams, permanent lakes, and intermittent lakes. Habitation sites were found to be signficantly more frequently associated with permanent springs than were other site types.
- D. L. True (1990; True and Waugh 1981, 1982) considered the influence of water on site locations on the northern tributaties of the San Luis Rey River between Lake Henshaw and Pala. Prehistoric water supplies in the drainages were inferred from the size of the watershed, the proportion of the watershed lying in the zone of higher precipitation above the 3200-foot elevation contour, and the permeability of the soils and bedrock in the streambed. According to True (1990:58), “by the late San Luis Rey II times, water became a signficant, if not critical, settlement determinant.” “The largest [San Luis Rey II] settlements were located near the best regional water supplies. Lesser sites…might well be ranked by size and importance, depending on the nature of the water resources for each village territory (tributaries). Unfortunately, the nuances of this specific proposal have not yet been adequately tested archaeologically” (True 1990:51). More irregular and intermittent settlement strategies in the earlier San Luis Rey I and Pauma periods were associated with the use of less optimal locations, although still with a bias toward sites that were favored with respect to water resources. A scarcity or absence of settlements located directly along the San Luis Rey River itself was explained by difficulties of access, the scarcity of level terrain for habitation sites, the need for a territorially neutral travel corridor to the coast, and mythologically reported dangers.
- Lynne E. Christenson’s (1990) settlement pattern study of southwestern San Diego County considered water source types (rivers, permanent streams, seasonal streams, and springs) and their distances from sites of various types. Sites were found to be significantly closer to water sources than sample non-site locations. Both kinds of locations were most frequently associated with seasonal streams than with other water sources, but sites were more frequently located near springs and rivers than were non-sites. Habitation sites were more strongly associated with relatively permanent water sources than were other site types.
- In a study of the archaeology of Otay Mesa, Mary Robbins-Wade (1990:100) suggested that “the availability of water was an important factor in determination of site locations. Resource procurement and processing ‘locations’ would not necessarily be near water, but residential bases and even temporary field camps would require its immediate availability.”
- Koji Tsunoda (2006) analyzed the spatial relationship between archaeological sites and water sources (including lakes, streams, creeks, and springs) in Cuyamaca Rancho State Park. Categorizing distances between sites and water sources in 100-m intervals, he found that the highest density of sites occurred in locations that were less than 100 m from the nearest water source.
- Jerry Schaefer and Don Laylander (2014; Laylander et al. 2015) analyzed archaeological site distances from mapped locations that presumably represented substantial water sources (including springs, perennial creeks, and third-order or higher drainages) in the Jacumba/McCain Valley region of southeastern San Diego County. Surprisingly, the locations of all sites and of habitation sites were found to be on average farther from water sources than were random points within the study region. Some categories of sites were disproportionately frequent within 1,000 m of water sources, but these represented only a small portion of the sites: 12% of all sites, and 16% of habitation bases. As expected, a greater frequency of proximity to water sources was found for sites with bedrock mortars.
PROSPECTS
Future archaeological investigations may be able to shed light on the extent to which the selection of site locations was influenced by the accessibility of water sources; on patterns of change through time in the influence of water availability, perhaps related to changes in technology, settlement strategy, or regional demography; on the relative importance of water availability for different site types; and on the relative importance of different types of water sources.
| Study, Location, and Main Chronological Period | Site Type | Number of Cases | Mean Distance to Water (m) |
| Cook and Fulmer 1980 (McCain Valley; Late Prehistoric) |
Habitation w/ midden | 18 | 80* |
| Milling Station | 18 | 400* | |
| Habitation w/o midden | 18 | 450* | |
| Ceramic Scatter | 31 | 540* | |
| Roasting Pit | 112 | 670* | |
| Lithic Scatter | 45 | 1040* | |
| Graham 1981 (Mt. Laguna; Late Prehistoric) |
Habitation | 28 | 214 |
| Processing | 78 | 214 | |
| Extraction | 6 | 252 | |
| Laylander and Christenson 1980 (Corral Canyon; Late Prehistoric) |
Large Habitation | 7 | 26 |
| Small Habitation | 8 | 34 | |
| Milling Station | 18 | 103 | |
| Rock Ring | 5 | 192 | |
| Lithic Scatter | 5 | 238 | |
| All Sites | 46 | 117 | |
| Non-Site Sample | 101 | 277 | |
| Christenson 1990 (western and southern San Diego County; Late Prehistoric) |
Large Habitation | 49 | 58 |
| Large Processing | 62 | 91 | |
| Small Habitation | 61 | 98 | |
| Large Lithic Scatter | 28 | 132 | |
| Quarry | 9 | 139 | |
| Small Processing | 166 | 164 | |
| Small Lithic Scatter | 16 | 216 | |
| Rock Alignment | 7 | 429 | |
| All Sites | 438 | 135 | |
| Non-Site Sample | 438 | 262 | |
| Robbins-Wade 1990 (Otay Mesa; Archaic) |
Residential Base | 12 | 92 |
| Field Camp | 21 | 193 | |
| Procurement/Processing | 131 | 323 |
* Distance from Rank II or higher streams or observed springs.