Plant Tour

Redwood Valley Area:

The District is very rural in nature with a very small, unincorporated town center. Land use is largely agricultural with most parcels between 5 acres and 60 acres. The remainder of the parcels under 5 acres with most of 1 acre minimums are residential parcels. There is very little commercial and industrial land use, most of which occupies the small town center.







Redwood Valley District consists of a wide, gently sloping valley bordered by mountains of the Coastal Range on the west and east. The West Fork of the Russian River bisects the District down the center of the valley from north to south. The boundary of the District extends up the hills to an elevation roughly equivalent to the storage reservoirs so that water delivery is mostly by gravity and only one booster pump station is required at the north end of the domestic distribution system.

The valley floor is an alluvial plain with a high clay content. The soils are non-porous and the valley has a deep groundwater table where it exists, if at all. There are occasional pockets of perched water in the alluvial soils, but none to provide a usable water supply. Extensive studies by the U. S. Geological Survey, Mendocino County Water Agency and the District have failed to develop a groundwater supply even close to the amount needed to sustain the District demand. Fractured bedrock from earthquake faults at the base of both mountain ranges may hold water, but it has been undiscovered to date and may be at great depth. Soil limitations that affect the use of water seem to provide soil types that are advantageous to agriculture, especially wine grapes.

The District experiences an inland coastal climate that is very similar to Mediterranean in nature. Average annual precipitation is about 40.0 inches with almost all received in the months of mid-October to mid-April. Maximum temperatures reach 110 F with an average of 20 days per year over 100 F for the daily high. Minimum temperatures reach 20 F with an average of 60 days per year below 32 F for the daily low. The prevailing wind direction is from the northwest to southwest. The wind direction in the winter, especially ahead of winter fronts, is from the southeast to south. The average wind velocity in the summer is a steady afternoon sea breeze of 18 20 mph. In the winter, steep pressure gradients between an inland low pressure system and an offshore high pressure system can reach gusts of 40 50 mph. Santa Ana conditions in the spring and fall can produce warm, dry easterly wind flows of 20 30 mph. The average number of frost free days annually is 300.

A somewhat different microclimate exists along the length of the West Fork of the Russian River and its tributaries in Redwood Valley where the cold air collects in the lowest elevations of the valley. Those areas of Redwood Valley reach freezing temperatures the earliest and require frost protection for longer periods than areas of the valley at higher elevations or on the upper benches. Some of the higher elevations of Redwood Valley may escape frost altogether even when frost is occurring at the lowest elevations. Before irrigation water was available from the District for frost protection, dry farming existed mainly at the higher, frost-free elevations. Agricultural customers in the lower elevations must have large enough private ponds to sustain them through longer periods of lower freezing temperatures. All areas of the valley are affected by high summer temperatures and overhead sprinklers are used to cool the vineyards, especially after several consecutive days of extreme high temperatures. During consecutive periods of long-duration frost or consecutive days of extreme heat, agricultural customers find it difficult to recharge their storage reservoirs satisfactorily. The District finds itself stretching the capabilities of its raw water pumping system in such extreme conditions by using two of its three - 500 HP pumps and running 24 hours daily to just keep pace with the demand. In such situations, the District has no system redundancy if its surge tank or transmission pipeline should fail or if more than one pump is not in operation. Also, the District has only 48 hours of storage in its 68 Acre Feet holding reservoir at peak demand conditions. The source of climate data came from the private records of a former District Manager from his 29 years of weather observations.

The West Fork of the Russian River and its tributaries, especially Forsythe Creek, are known rivers and streams within the District. Lake Mendocino is an artificial lake that lies outside the District boundary but is the water supply for the District. None of these known natural resources are managed by the District at the present time.

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