چارچوب مفهومی برای تخمین امکان سنجی اقتصادی بانکی زیرزمینی در زمین های کشاورزی
Abstract: Since 1865 California has practiced underground water storage through artificial recharge; however, in many parts of the state these efforts have been insufficient to meet its growing water demands, particularly for irrigated agriculture. During dry periods, vast agricultural areas depend upon groundwater for irrigation. In these areas, groundwater banking (GB) should be an essential strategy of their water management operations. GB is the practice of using surface water for percolation or injection into aquifers for later recovery. One variation of GB currently being studied in California is the use of agricultural lands for this practice (Ag-GB). Economic implications of Ag-GB need to be analyzed to inform water agencies and farmers interested in implementing this practice. This study proposes a conceptual model for determining the economic feasibility of Ag-GB at the irrigation district level. The Orland-Artois Water District (OAWD) in Glenn County is considered as the case study, and alfalfa as the test crop due to its tolerance to flooding and low use of pesticides and fertilizers which could leach into the aquifer. The proposed model consists of four components. The first component, the agricultural water demand calculator, calculates agricultural water demands based on historic land use, monthly reference evapotranspiration (ETo), monthly average precipitation, and average crop coefficient (Kc) values for the region. The second component, the aquifer mass balance model, is a one-bucket mass balance model that quantifies inflows and outflows to the simplified aquifer. The third component, the agronomic model, estimates costs and benefits of Ag-GB in terms of energy savings from pumping and crop production. The fourth component, the economic feasibility output, evaluates costs and benefits are evaluated to determine economic feasibility. The period of analysis is from 1993 through 2013. Two policies (A and B) for implementation of Ag-GB are proposed and tested. Policy A proposes that all growers in OAWD pay for the implementation of the Ag-GB program. Policy B proposes that alfalfa growers using their lands for Ag-GB (Ag-GB alfalfa growers) are exempted from paying for Ag-GB implementation and the rest of the growers (non Ag-GB growers) pay for it. The economic analysis suggests that Policy A brings more costs than benefits to the Ag-GB alfalfa growers and hence is rejected as feasible. Policy B seems to bring more benefits than costs to all growers in OAWD and therefore it has potential to be economically feasible under the assumptions and limitations of the model.
Keywords: Agronomics,Economic feasibility,Groundwater banking,Water management, Water mass balance