Hydrologic impacts of small‐scale instream diversions for frost and heat protection in the California wine country

Abstract

Though many river studies have documented the impacts of large water projects on stream hydrology, few have described the effects of dispersed, small-scale water projects on streamflow or aquatic ecosystems. We used streamflow and air temperature data collected in the northern California wine country to characterize the influence of small instream diversions on streamflow. On cold spring mornings when air temperatures approached 08C, flow in streams draining catchments with upstream vineyards receded abruptly, by as much as 95% over hours, corresponding to times when water is used to protect grape buds from freezing; flow rose to near previous levels following periods of water need. Streams with no upstream vineyards showed no such changes in flow. Flow was also depressed in reaches below vineyards on hot summer days, when grape growers commonly use water for heat protection. Our results demonstrate that the changes in flow caused by dispersed small instream diversions may be brief in duration, requiring continuous short-interval monitoring to adequately describe how such diversions affect the flow regime. Depending on the timing and abundance of such diversions in a drainage network, the changes in streamflow they cause may be an important limiting factor to valued biotic resources throughout the region.

Effects of vineyard coverage and extent on benthic macroinvertebrates in streams of Northern California

“…The effect of water withdrawals for frost protection on streamflow differed among the three streams examined (Deitch et al, 2009). In 2005, when the most complete streamflow records were kept at the three sites, the reduction of streamflow observed was by far the highest in Franz Creek (Tab.…”

“…These reductions typically occur between the months of March and April (Deitch et al, 2009), which coincides with the end of the rainy season in this region (Gasith and Resh, 1999). This time period is very important for the resident benthic macroinvertebrates because it is when the majority of preemergence growth occurs (Mendez and Resh, 2008).…”

“…Use of water sprinklers for frost protection has been observed repeatedly to drastically reduce streamflow in small streams in the Mediterranean-climate region of Northern California (Deitch et al, 2009). These reductions typically occur between the months of March and April (Deitch et al, 2009), which coincides with the end of the rainy season in this region (Gasith and Resh, 1999).…”

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“…Os biólogos da década de 1970 e 1980 acreditavam que vazões elevadas em períodos de secas garantiriam melhor qualidade de vida aos peixes. Entretanto, na visão atual, observa-se que os modelos que se aproximam do regime de fluxo natural de um rio, garantem melhor qualidade de vida para flora e fauna aquáticas (Chang et al, 2008, Sanderson et al, 2008Deitch et al, 2009a), pois vazões altas podem beneficiar determinada espécie, mas comprometer outras e vice-versa (King et al, 2008).…”

“…Poff et al (1997) citam que a variabilidade hidrológica é influenciada pela magnitude, duração, frequência e época de ocorrência de vazões mínimas e máximas (Jacobson e Galat, 2006;Neubauer et al, 2008;Masih et al, 2009;Gao et al, 2009;Wen, 2009; Zeilhofera e Moura, 2009), ilustrativamente observadas em Bunn e Arthington (2002) (Tucci 2009, Naiman et al, 2008, em que se destacam quatro princípios sobre a influência do regime natural de vazões na biodiversidade ripária mediante vários mecanismos relacionados no tempo e no espaço, resumidamente expressos em um hidrograma, atentando-se: às relações MEDEIROS, P. C.; SOUZA, F. A. S.; RIBEIRO, M. M. R. Aspectos conceituais sobre o regime hidrológico para a definição do hidrograma ambiental. Ambi-Agua, Taubaté, v. 6, n. 1, p. 131-147, 2011 Deitch et al, 2009a;Deitch et al, 2009b), especialmente nas secas prolongadas, considerando-se as prioridades ecológicas, o comportamento do fluxo e a limitação/interrupção para explotação de água. Heicher (1993 apud Smakhtin, 2001), esboçou vários efeitos ambientais causados pela redução no escoamento de base (aumento da sedimentação, alterando a morfologia do canal, distribuição da biota, aumento da temperatura e penetração dos raios de sol, mudanças na densidade, produtividade, e composição de espécies).…”