Rapid economic development has posed pressure on water resources, and the potential for a water crisis has become an important obstacle to the sustainable development of society. Water footprint theory and its applications in agriculture provide an important strategic basis for the rational utilization and sustainable development of water resources. Based on the monthly meteorological observations and agricultural data of Shandong Province, CROPWAT 8.0 and Geographic Information System (GIS) technology, the green, blue and grey water footprints of wheat, maize, cotton and groundnut from 1989 to 2016 were calculated and the spatial variations of water footprints for crops in different rainfall years were analyzed. Additionally, assessment of water stress for agricultural productions was conducted in this study. The results showed that the average water footprints of wheat, maize, cotton and groundnut were 2.02 m³/kg, 1.24 m³/kg, 7.29 m³/kg and 1.75 m³/kg, respectively in Shandong Province. A large amount of the average total water footprint was calculated for wheat (420.59 × 10⁸ m³/yr), maize (222.16 × 10⁸ m³/yr), cotton (72.70 × 10⁸ m³/yr) and groundnut (50.07 × 10⁸ m³/yr). The average total water footprint of the four crops was 765.52 × 10⁸ m³/yr (29.98% blue) and exhibited a gradual decreasing trend over time. Specifically, the total water footprint of wheat was the highest among four main crops in Shandong Province and exhibited a decreasing trend during 1989–2016. The maize was ranked in the second place, and was the only crop still increasing rapidly. The spatial and temporal changes of water footprints for crops were obvious in different rainfall years. Additionally, agricultural productions in most regions were facing the threat of water scarcity. Therefore, the scientific planning of crop planting structures and rational control of sown areas of crops with large water footprints should be implemented in severely water-scarce regions. This study can give some suggestions on the adjustment of planting structure for the sustainable development of agriculture and the realization of efficient utilization of water resources.

(1) Background: As a halophytic species, Tamarix (Tamarix chinensis) can be used for saline soil rehabilitation in China. The reclamation and rehabilitation of saline soil depend on the water consumption of plants. However, whether water resources in saline soil can support the construction of Tamarix vegetation is still unknown. (2) Methods: In this study, we measured the transpiration (T) of Tamarix for 3 years using sap flow and the evaporation (E) for 1 year using a micro-lysimeter in Tamarix land. The evaporation values in 2016 and 2017 were estimated with the soil crop coefficients obtained in 2018. (3) Results: The evapotranspiration (ET) ranged from 514.2 to 573.8 mm and was greatly affected by the wind speed, VPD and groundwater table. Transpiration was the main form of water consumption in this region, accounting for 60.2% of the total evapotranspiration. Compared with bare land, vegetation construction increased soil moisture dissipation by 377.6 mm in 2018. According to on-site measurements and estimates, the water shortage in the dry year was 107.2 mm, and the residual water values in the normal year and wet year were 77.8 mm and 187.5 mm, respectively. May and September were months of widespread water shortages in different precipitation years. Although the cultivation of this plant increased water consumption, the groundwater table remained at approximately 0.5 m during the study year. (4) Conclusions: These results indicated that planting Tamarix in coastal saline soil was feasible for the reclamation and rehabilitation of saline soil. In the dry year (2017), the consumption of evapotranspiration exceeded the precipitation. The inverse occurred in the normal year (2016) and wet year (2018). Taken together, our findings showed that the water resources in the coastal saline soil of China could tolerate vegetation construction and laid a strong foundation for saline soil rehabilitation.