Runoff variation and its response to climate change in Huolin River catchment,Northeast China

The Huolin River catchment(HRC)is located in the semi-arid region of Northeast China,which is very sensitive to climate change.The runoff in HRC is closely related to the recovery of local vegetation in the Greater Khingan Mountains and the survival of downstream wetlands.Dramatic runoff fluctuations and increasing no-flow days confirmed the water crisis in this area.Hence,it is extremely urgent to study the current situation and characteristics of runoff.In this study,hydrological and meteorological data of HRC during 1956-2018 were analyzed to elucidate the processes,characteristics,trends of the river runoff and revealed its response to climate change.The Mann-Kendall test and linear regression method showed that runoff in the HRC demonstrated a downward trend over the study period with a marked annual variation.The runoff in the high flow years was 100 times that of the low flow years,showing a typical continental climatic river characteristic.There are two runoff peak flows in the intra-annual runoff distribution in March and July,whereas two runoff valleys occurred around May and September to February.The runoff positively correlates with precipitation in summer and temperature in early spring.Snowmelt influenced by rising temperatures in April and precipitation in July is the main driving factor for the two peaks flow.Evaporation rose with precipitation decline and temperature increased,which may influence the runoff decrease.The annual runoff is well synchronized with the annual precipitation,and precipitation change is the main driving factor of variation and abrupt change points of annual runoff in the catchment.This study would be beneficial for water resource management in developing adaptation strategies to offset the negative impact of climate change in HRC.

Tidal Response Characteristics of the Well Water Level in the Sichuan-Yunnan Region

In this paper,the long time series data of the well water-level data of 12 wells in the Sichuan and Yunnan area is analyzed by the Baytap-G tidal analysis software,and well water level tidal response characteristic parameters( amplitude ratio and phase change)are extracted. We analyzed the features of the shape and stage change,and characteristic parameters of the tidal response of well water level before and after the earthquakes,which can provide a new method and approach to analyzing the response relationships between well water level and earth tide and barometric pressure. The results show that Luguhu Well and 9 other wells are affected by earth tides,and their well water level amplitude ratios and phases are relatively stable; the Nanxi Well and Dayao Well water level changes are affected by the barometric pressure combined with tide force,and their well water level amplitude ratios and phases are more discrete. The water level amplitude ratios and phases of Jiangyou Well,Luguhu Well and Dongchuan Well are significant to large earthquakes,and the relationship between seismic energy density and water level amplitude ratios and phases of M_2 wave of the three wells are presented.

Spatial distribution of maize in response to climate change in northeast China during 1980–2010

Based on county-level crop statistics and other ancillary information, spatial distri- bution of maize in the major maize-growing areas （latitudes 39°-48°N） was modelled for the period 1980-2010 by using a cross-entropy-based spatial allocation model. Maize extended as far north as the northern part of the Lesser Khingan Mountains during the period, and the area sown to maize increased by about 5 million ha. More than half of the increase occurred before 2000, and more than 80% of it in the climate transitional zone, where the annual ac- cumulated temperature （AAT） was 2800-3400 ℃.d. Regions with AAT of 3800-4000 ℃-d became more important, accounting for more than 25% of the increase after 2000. The ex- pansion of maize was thus closely related to warming, although some variation in the distri- bution was noticed across zones in relation to the warming, indicating that maize in northeast China may have adapted successfully to the warming by adjusting its spatial distribution to match the changed climate.