Davids Engineering Inc.

Davis, CA, United States

Davids Engineering Inc.

Davis, CA, United States

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Steele D.D.,North Dakota State University | Thoreson B.P.,Davids Engineering Inc. | Hopkins D.G.,North Dakota State University | Clark B.A.,Davids Engineering Inc. | Tuscherer S.R.,North Dakota State University
Irrigation Science | Year: 2014

Excessive precipitation since 1993 has produced extensive flooding in the Devils Lake basin in northeastern North Dakota, USA. Irrigation of agricultural crops has been proposed as a flood mitigation tool. Ten test fields were equipped with center pivot irrigation systems to compare test field evapotranspiration (ET) with ET for crops in the predominantly nonirrigated basin. An irrigation scheduling analysis indicated 2006 was a favorable year to estimate the maximum ET gains achievable via irrigation. An ET map for 2006 using the Surface Energy Balance Algorithm for Land (SEBAL) for 54 % of the basin, and land use and soil survey data, was used to compare ET estimates at the test fields with ET estimates across the study area. May–September ET was estimated by SEBAL as 394 mm for wheat and 435 mm for corn across the study area, while corn ET at irrigated test sites was 452 mm. Because the 17-mm ET advantage by irrigating corn was substantially smaller than the 41-mm ET advantage for corn versus wheat, we conclude widespread irrigation development to mitigate flooding is not justified. Coarse-textured soils exhibited some seasonal ET deficits, but their small areal extents and parcel sizes offer virtually no opportunity for flood mitigation. © 2014 Springer-Verlag Berlin Heidelberg.


Davids J.C.,Davids Engineering Inc. | Davids J.C.,California State University, Chico | Mehl S.W.,California State University, Chico
Groundwater | Year: 2015

Most surface water bodies (i.e., streams, lakes, etc.) are connected to the groundwater system to some degree so that changes to surface water bodies (either diversions or importations) can change flows in aquifer systems, and pumping from an aquifer can reduce discharge to, or induce additional recharge from streams, springs, and lakes. The timescales of these interactions are often very long (decades), making sustainable management of these systems difficult if relying only on observations of system responses. Instead, management scenarios are often analyzed based on numerical modeling. In this paper we propose a framework and metrics that can be used to relate the Theis concepts of capture to sustainable measures of stream-aquifer systems. We introduce four concepts: Sustainable Capture Fractions, Sustainable Capture Thresholds, Capture Efficiency, and Sustainable Groundwater Storage that can be used as the basis for developing metrics for sustainable management of stream-aquifer systems. We demonstrate their utility on a hypothetical stream-aquifer system where pumping captures both streamflow and discharge to phreatophytes at different amounts based on pumping location. In particular, Capture Efficiency (CE) can be easily understood by both scientists and non-scientist alike, and readily identifies vulnerabilities to sustainable stream-aquifer management when its value exceeds 100%. © 2015, National GroundWater Association.


Mendez-Costabel M.,EandJ Gallo Winery | Morgan A.,EandJ Gallo Winery | Dokoozlian N.,EandJ Gallo Winery | Thoreson B.,Davids Engineering Inc. | Clark B.,Davids Engineering Inc.
Acta Horticulturae | Year: 2014

Field measurements of basal crop coefficients (Kc) were taken during the 2001 season in order to validate the energy balance algorithm at the land level (SEBAL) in multiple commercial vineyards located within the Central Valley of California. For this purpose, we used estimates of crop coefficients (ETa/ETo), basal crop coefficients (ETp/ETo), and NDVI, all derived by SEBAL North America from Landsat TM 5 images collected at different times during the growing season. Since vineyard evapotranspiration (ETa) is affected by the interaction between irrigation levels and atmospheric demand we focused on potential water use (ETp) and basal crop coefficients (Kc=ETp/ETo). The basal crop coefficients obtained from SEBAL were compared with field measurements of potential water use collected over several locations in multiple commercial vineyards. The results showed a very good accuracy of the SEBAL model (error +/-5% across multiple vineyards and varieties). We also looked at the relationship between basal crop coefficients and NDVI, and then studied the link between NDVI and vineyard parameters such as yield, and soluble solids. NDVI and basal crop coefficients for almost two hundred commercial vineyards were analyzed covering a very wide range of the two variables, which were found to be highly correlated (r2>0.95) However, NDVI did not correlate very well with either yield or fruit composition variables such as soluble solids.


PubMed | California State University, Chico and Davids Engineering Inc.
Type: Journal Article | Journal: Ground water | Year: 2015

Most surface water bodies (i.e., streams, lakes, etc.) are connected to the groundwater system to some degree so that changes to surface water bodies (either diversions or importations) can change flows in aquifer systems, and pumping from an aquifer can reduce discharge to, or induce additional recharge from streams, springs, and lakes. The timescales of these interactions are often very long (decades), making sustainable management of these systems difficult if relying only on observations of system responses. Instead, management scenarios are often analyzed based on numerical modeling. In this paper we propose a framework and metrics that can be used to relate the Theis concepts of capture to sustainable measures of stream-aquifer systems. We introduce four concepts: Sustainable Capture Fractions, Sustainable Capture Thresholds, Capture Efficiency, and Sustainable Groundwater Storage that can be used as the basis for developing metrics for sustainable management of stream-aquifer systems. We demonstrate their utility on a hypothetical stream-aquifer system where pumping captures both streamflow and discharge to phreatophytes at different amounts based on pumping location. In particular, Capture Efficiency (CE) can be easily understood by both scientists and non-scientist alike, and readily identifies vulnerabilities to sustainable stream-aquifer management when its value exceeds 100%.

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