Conflicting water requirements may exist between agricultural and natural ecosystems. In order to relieve conflicts, we have proposed a method of determining standards for ecological compensation by giving priority to environmental flows in water allocation. Agricultural water quota was considered in the calculation of agricultural water shortage. A water production function model was introduced to determine the relationship between agricultural water shortages and production losses. The ecological compensation standard for agricultural areas was determined by multiplying production losses by the unit crop price. Due to the seasonality of the runoff process and environmental flows, the ecological compensation standard showed annual and seasonal variation. We calculated the ecological compensation standard for summer corn and winter wheat irrigation stakeholders in the Shandong irrigation district, after ensuring environmental flows in the Yellow River Estuary. The amount of agricultural water usage was more than the water quota between June and September. This meant that securing a high level of environmental flow had no influence on summer corn production. However, water conflict during the growth stage of winter wheat caused a 1611.77 kg/hm² reduction in yield, accounting for 31.70% of maximum production. The calculated annual average economic compensation was 1826.92 Yuan/hm² for winter wheat irrigation stakeholders in the Shandong irrigation district of the Yellow River between 1998 and 2005.
The agricultural water shortage exhibited annual and seasonal variation due to the combined influences of environmental flow and runoff. In general, the higher the environmental flow, the more likely an agricultural water shortage. The level of the agricultural water shortage was 0-10 × 10⁸ m³, 0-20 × 10⁸ m³, and 20-70 × 10⁸ m³, when minimum, medium, and maximum levels of environmental flow were ensured.
Economic compensation showed similarly obvious differences after ensuring a certain level of environmental flow. The scope of the economic compensation was 0-1600, 0-3100, and 1000-9000 Yuan/hm² when minimum, medium, and maximum environmental flows were ensured. Economic compensation also showed annual and seasonal variation due to the combined influences of environmental flow, runoff, and crop yield response factors. It is advisable to determine the environmental flow level after fully considering the amount of runoff.
Variation in the runoff process and environmental flow requirements should be taken into account when determining different levels of ecological compensation. The selection of typical crops will influence the calculation of economic compensation. We selected winter wheat and summer corn as examples, as these have the largest planting areas in the Shandong irrigation district. The water resource value was 1.16 Yuan/m³ after ensuring the maximum environmental flow; lower than in other domestic cases but higher than in foreign studies. Foreign studies have calculated economic compensation in a cost-minimizing fashion. The crop with the lowest unit of water value has been used as the starting point. However, this is not the only criterion for crop selection. Typical food crops, which have a stable planting area and significant water needs, are suitable for use in determining standards for ecological compensation in agricultural areas.