#Starcrossed 1985 review series
Numerical simulations are currently the most widely used to quantify baseflow because the models are easy to operate and suitable for long-term hydrologic series 23. Methods used for baseflow separation are limited to hydrograph analysis, which utilizes existing river flow data and provides estimates of baseflow without the need for complex modeling, detailed knowledge of soil characteristics, or costly site investigations 22. Baseflow is difficult to measure directly compared with runoff. Human interferences, such as land use and land cover changes, water flow or storage through river diversions, and groundwater pumping, affect the baseflow recession process.
There is still a lack of research, especially on the characteristics of base flow change and its influencing factors 21. The responses of base flow to climate change and anthropogenic activities are different. Therefore, understanding the role of base flow in the streamflow processes is critical for the quantifying and identifying direct runoff and groundwater storage 17, 18, 19, 20.
In arid and semiarid areas, streamflow is mainly supplied by baseflow, making baseflow an important hydrologic characteristic 15, 16. Streamflow is the most important component of the hydrological cycle and is typically divided into two components for hydrograph separation: base flow and quick flow or storm flow. 13, Budyko 14) assessed the impacts of climate change and human activities on hydrological processes. 11) and a method based on the water-energy balance (for instance, Ma et al. Many studies have used conceptual, physical, black-box numerical models and empirical statistics (for instance, Zhang et al. Therefore, Understanding the influence of climate variability and human activities will be beneficial for developing sustainable water management strategies. In these water‐limited areas, Human interferences and climate change impact are of increasing apprehension for water resource strategists and managers. However, these regions support about 20% of the global population 5. The water resources of the semiarid regions account for less than 2% of the global total 4. Climate variability have led to global warming and changing precipitation patterns, while human activities have changed the temporal and spatial distribution of water resources 1, 2, 3.
The baseflow index trend and elasticity estimation also indicated that intensive human activities had more significant effects on the Dez Basin's hydrological processes and streamflow variation.Ĭlimate change and anthropogenic activities are two major factors that impact hydrological processes. The maximum change occurred in the sub-basin tireh which after change point from 1977 to 1993,runoff reduced − 1.49% comparison with the base period( from 1967 to 1976) also elasticity estimation was − 0.46,but after change point in Baseflow index from 1994 to 2016 runoff reduced − 55.02% and elasticity estimation was − 0.65.
The abrupt change point was determined after the change in the BFI index the runoff was reduced. Additionally, at the seasonal scale in these sub-basins, the average precipitation in winter showed a significant downward trend, while runoff showed a decreasing trend and the BFI index showed increasing trends in winter, spring and summer. Furthermore the analyzed trend test at the annual scale showed a significant decreasing trend for runoff as well as increasing trends for the baseflow index in the four of five sub-basins of the Dez River at confidence levels of 95% and 99%, while the average precipitation in these sub-basins was not significant. The results of the separation methods showed that the sliding interval method produced a better performance. Then, the elasticity coefficient method was applied to calculate the impacts of natural factors and anthropogenic activities. Second, the Mann–Kendall trend test was used to identify trends and change points. In this study, we first used the Hydrograph Separation Program to separate and analyze the base flow index (BFI) that was impacted directly by human activity and precipitation as an important climate factor from 1967 to 2016 in the Dez River Basin. Assessment of streamflow variations under the influence of climate change and human activity is crucial for sustainable water resource management, especially in semiarid areas.