We found that individuals with knowledge and educational background were less affected by the framing. In a negatively framed questionnaire, knowledge increased the perception that GMFs are healthier, whereas in a positively framed questionnaire, knowledge did not affect perceptions. Estimating the choice process of GMFs versus traditionally grown bell peppers when GM bell peppers are sold at a 30% discount revealed that the perceptions that biotechnology con tributes to health and reduces pesticide use were the only salient attributes in the decision process. Positive framing did have a statistically significant effect on the weights given to health and taste in the decision process. While negative framing decreased the weight attributed to the health benefits of GMF consumption and increased the weight of taste in the choice process, there is also significant joint effect. Moral considerations increased support at low statistical significance while gender and knowledge did not make a difference at all. This is in contradiction to other studies where females have more negative perceptions about GMFs than men. The predictive power of socioeconomic factors is rather low. Summarizing the aforementioned findings suggests that if the information is negatively framed, then the weight assigned to health increases and that of taste decreases. Since perceptions of healthiness and tastiness decline with negative framing, the increase in the weight assigned to health amplifies the effect of negative framing. Education did not make a difference in the preference of GMFs in cases with 30% and 5% dis counts. These results did not change much when GMFs were offered at a 5% discount,growing blueberries in containers and motivation for acceptance of GMFs was altered to better taste, longer shelf life, and less pesticide use.
California is experiencing its third major drought since the 1970s, and projections suggest that such episodes will become longer and more frequent in the second half of the 21st century . Droughts place more demand on groundwater resources to buffer surface water shortfalls. Ordinarily, about 30% of the water applied to crops in California is supplied by groundwater sources, but in times of drought the proportion can increase to as much as 60% . As a result, groundwater levels fall during droughts . If groundwater is not replenished during wet years, long-term overdraft occurs. From 2005 through 2010, average annual overdraft in the Central Valley was estimated to be between 1.1 and 2.6 million acre-feet . Two recent trends in California have tended to increase the rate of groundwater overdraft in agricultural regions. First, over the past two decades, irrigation technologies have significantly improved water use efficiencies . Where surface water is used for irrigation, a consequence of applying less water is that groundwater recharge is diminished because of a reduction in deep percolation of excess water. Second, expanding worldwide markets have driven significant expansions of nut and wine grape acreage. For example, the almond acreage in California has doubled, to roughly 1 million acres, since 1994 . Much of this expansion has occurred in the San Joaquin Valley where rates of rainfall and natural groundwater recharge are low. This shift in cropping systems to high value perennial crops reduces the flexibility of agricultural water demand because the economic costs of not irrigating are severe. Inflexible demand has made agriculture even more reliant on groundwater during dry periods when surface water resources are curtailed.Natural groundwater recharge is the predominant source of groundwater replenishment in almost all basins. It is typically unmanaged and can be slow. Water percolates into aquifers from a variety of surface water sources including precipitation, streams, rivers, lakes, surface water conveyance facilities — such as unlined canals — and applied irrigation water. Natural recharge also may occur from horizontal subsurface inflow from one part of a groundwater basin to another. Natural recharge requires no dedicated infrastructure or land.
Groundwater banking is a management strategy that stores surface water in aquifers for future withdrawal. It expands managed water storage capacity, which in California consists mainly of surface water reservoirs.During hydrologic cycles when surface water is abundant, extra surface water can be “deposited” in a groundwater bank by application to constructed percolation basins, through injection wells, or through joint management of rivers and groundwater to effect riverbed infiltration into underlying aquifers. A key limitation to groundwater recharge is the lack of suitable percolation basins available for deliberate flooding. In this paper, we consider a new strategy for groundwater banking that involves applying water to agricultural lands outside of the usual irrigation season for the specific purpose of recharging a groundwater basin. Given the millions of acres of irrigated farmland in California, using agricultural lands as percolation basins has the potential to increase groundwater recharge during wet periods when surface water is available. In California, one potential source of water for recharge on agricultural land is river floodwaters, because surface water rights may be easily re-negotiated for the excess water. This floodwater approach has the dual benefit of withdrawing large amounts of water from a river that is at or near flood stage and reducing downstream flood risks . The frequency and intensity of river flooding is difficult to forecast. For instance, flood flows on the Kings River from 1975 to 2006 had an average reoccurrence interval of 2 to 3 years, though flooding has not occurred in recent years . As the climate warms, flooding may become more frequent and extreme as a result of episodic snow melt events driven by warm winter rains. Recycled water is another potential source. There are a variety of institutional and other barriers to widespread agricultural groundwater banking in California. Water rights for operation of aquifers as reservoirs are challenging to navigate; water conveyance infrastructure has limited capacity; regional planning to capture river flood waters may be difficult to organize; fields with high percolation rates at the surface may be underlain by low-percolation layers that slow or block the recharge of deeper aquifers; it can be difficult to assess how much capacity a given aquifer has to store banked groundwater; certain crops and certain stages of crop growth do not tolerate flooded conditions; and the quality of water recharged to an aquifer via agricultural land may be degraded due to excessive leaching of contaminants from soil such as pesticides and nitrates.
To date, few well-documented trials of groundwater banking have been conducted on agricultural land. Since nearly all agricultural land is privately owned and operated, participation in groundwater banking programs depends on cooperation from the landowner or land manager. Therefore, a clear understanding of the risks and best practices associated with this practice is paramount. In this study, we take a first step toward better understanding opportunities to recharge groundwater using agricultural landscapes in California by identifying and mapping the soil and topographic conditions most conducive to groundwater recharge.This study developed a Soil Agricultural Groundwater Banking Index that provides a composite evaluation of soil suitability to accommodate groundwater recharge while maintaining healthy soils, crops and a clean groundwater supply. The SAGBI is based on five major factors that are critical to successful agricultural groundwater banking: deep percolation,square pots root zone residence time, topography, chemical limitations and soil surface condition .Successful groundwater banking depends on a high rate of water transmission through the soil profile and into the aquifer below. A high percolation rate is especially important if floodwaters are the water source used because floodwaters are available for diversion over a narrow time frame. The deep percolation factor is derived from the saturated hydraulic conductivity of the limiting layer . Saturated hydraulic conductivity is a measure of soil permeability when soil is saturated. Many soils in California have horizons with exceptionally low Ksat values that severely limit downward percolation, such as cemented layers , claypans and strongly contrasting particle size distributions. Soils with these horizons were given crisp scores of 1. For other soils, a “more is better” fuzzy logic rating curve was applied to a soil profile’s lowest Ksat to score the likelihood of deep percolation . Prolonged duration of saturated or nearly saturated conditions in the root zone can cause damage to perennial crops, and in some cases, crop loss . About one third of California’s irrigated cropland is occupied by perennial crops and vines. Table 1 provides estimates of tolerance to saturation for some common tree and vine crops before and after bud break compiled through a survey of UC ANR Cooperative Extension commodity experts. Annual crops were not included in the survey because we assumed that these fields generally would be fallow during times of excess surface water availability. In general, crops become prone to damage after bud break and there is a range in tolerance among crops and root stocks . For example, wine grapes and pears may be able to withstand more than two weeks of saturated conditions before bud break, while avocados and citrus have no tolerance. Our survey identified that many crops are unable to withstand long periods of saturated conditions in the root zone. To account for this potential adverse outcome, we included in the model a saturation residence time factor for soils. The root zone residence time factor estimates the likelihood of maintaining good drainage within the root zone shortly after water is applied. This rating is based on the harmonic mean of the Ksat of all horizons in the soil profile, soil drainage class and shrink-swell properties. The harmonic mean is typically used when reporting the average value for rates and tends to be lower than a standard average.
Poorly drained soils and soils with high shrinks well received the lowest scores with a crisp rating of 1.Groundwater banking by flood spreading can subject the soil surface to changes in its physical condition. Depending on the quality of the water and depth of water, standing water can lead to the destruction of aggregates, the formation of physical soil crusts and compaction, all of which limit infiltration . We used two soil properties to diagnose surface condition, the soil erosion factor and the sodium adsorption ratio . The surface condition factor was calculated by the geometric mean of fuzzy logic scores from these two properties. A geometric mean is a way to identify the average value of two or more properties that have different ranges in value. SAR values greater than 13 indicate that the soil is prone to crusting. A “less is better” fuzzy logic curve was used to evaluate SAR, where values greater than 13 were assigned a crisp rating of 1, and values of 0 were assigned an optimal rating of 100. Soil surface horizon Kw, the soil erodibility factor of the Revised Universal Loss Equation, was used to estimate the potential soil susceptibility to erosion, disaggregation and physical crust formation . A fuzzy logic rating curve, “optimum and less is better,” was used for scoring the surface condition factor. Kw values < 0.20 were considered ideal ; beyond this threshold, factor scores decreased with increasing Kw values. In recent decades, high value orchard and vineyard crops have expanded onto soil landscapes that contain restrictive horizons. A standard practice for tree and vine establishment on these soils is deep tillage up to a depth of 6 feet to destroy restrictive layers that impede root penetration. This practice increases deep percolation rates and drainage conditions compared to naturally occurring soils. Soils with root- and water-restrictive horizons in California have been altered to the point that they are now considered endangered in the Central Valley . As a result, soil surveys of much of the region — many of which were conducted decades ago — are outdated with respect to alterations by deep tillage. To address this problem, we created an updated soil disturbance map using geospatial analysis. A map of orchard and vineyard crops was created using California Department of Water Resources land use maps and aerial imagery from the National Agricultural Imagery Program and Google Earth . This file was overlain in a geographic information system with a map of soils with water-restrictive horizons. We assumed that all tree and vine cropland with restrictive soil layers has been modified by deep tillage, generating an updated map of modified soils.