The behavior of specific sediment yield in different grain size fractions in the tributaries of the middle Yellow River as influenced by eolian and fluvial processes

Based on data from 35 stations on the tributaries of the Yellow River, annual specific sediment yield (Y_s) in eight grain size fractions has been related to basin‐averaged annual sand–dust storm days (D_ss) and annual precipitation (P_m) to reveal the influence of eolian and fluvial processes on specific sediment yield in different grain size fractions. The results show that Y_s in fine grain size fractions has the highest values in the areas dominated by the coupled wind–water process. From these areas to those dominated by the eolian process or to those dominated by the fluvial process, Y_s tends to decrease. For relatively coarse grain size fractions, Y_s has monotonic variation, i.e. with the increase in D_ss or the decrease in P_m, Y_s increases. This indicates that the sediment producing behavior for fine sediments is different from that for relatively coarse sediments. The results all show that Y_s for relatively coarse sediments depends on the eolian process more than on the fluvial process, and the coarser the sediment fractions the stronger the dependence of the Y_s on the eolian process. The Y_s–D_ss and Y_s–P_m curves for fine grain size fractions show some peaks and the fitted straight lines for Y_s–D_ss and Y_s–P_m relationships for relatively coarse grain size fractions show some breaks. Almost all these break points may be regarded as thresholds. These thresholds are all located in the areas dominated by the coupled wind–water process, indicating that these areas are sensitive for erosion and sediment production, to which more attention should be given for the purpose of erosion and sediment control. A number of regression equations were established, based which the effect of rainfall, sand–dust storms and surface material grain size on specific sediment yield can be assessed. Copyright © 2007 John Wiley & Sons, Ltd.     

A study of scale effect on specific sediment yield in the Loess Plateau,China

Based on data from 148 hydrometric stations in the Yellow River Basin, an analysis of regional scale relationship, or the relationship between specific sediment yield and drainage basin area, has been undertaken in the study area of the Loess Plateau. For different regions, scale relationship in log-log ordinate can be fitted by two types of lines: straight and parabola, and for each line, a function was fitted using regression analysis. The different scale relationships have been explained in terms of the difference in surface material distribution and landforms. To offset the scale-induced influence, calcu-lation has been done based on the fitted functions, in order to adjust the data of specific sediment yield to a common standard area. Based on the scaled data, a map of specific sediment yield was con-structed using Kriging interpolation. For comparison, a map based on the un-scaled data of specific sediment yield was also constructed using the same method. The two maps show that the basic pattern of specific sediment yield was basically the same. The severely eroded areas (Ys >10000 t km-2a-1) were at the same locations from Hekouzhen to Longmen in the middle Yellow River Basin. However, after the adjustment to a common standard area, the very severely eroded area (Ys >20000 t km-2a-1) became much enlarged because after the adjustment, all the values of Ys in the lower river basin in those regions became much larger than before.     

Estimation of maize yield by using a process-based model and remote sensing data in the Northeast China Plain

Climate change significantly impact on agriculture in recent year, the accurate estimation of crop yield is of great importance for the food security. In this study, a process-based mechanism model was modified to estimate yield of C₄ crop by modifying the carbon metabolic pathway in the photosynthesis sub-module of the RS–P–YEC (Remote-Sensing–Photosynthesis–Yield estimation for Crops) model. The yield was calculated by multiplying net primary productivity (NPP) and the harvest index (HI) derived from the ratio of grain to stalk yield. The modified RS–P–YEC model was used to simulate maize yield in the Northeast China Plain during the period 2002–2011. The 111 statistical data of maize yield from study area was used to validate the simulated results at county-level. The results showed that the Pearson correlation coefficient (R) was 0.827 (p < 0.01) between the simulated yield and the statistical data, and the root mean square error (RMSE) was 712 kg/ha with a relative error (RE) of 9.3%. From 2002 to 2011, the yield of maize planting zone in the Northeast China Plain was increasing with smaller coefficient of variation (CV). The spatial pattern of simulated maize yield was consistent with the actual distribution in the Northeast China Plain, with an increasing trend from the northeast to the southwest. Hence the results demonstrated that the modified process-based model coupled with remote sensing data was suitable for yield prediction of maize in the Northeast China Plain at the spatial scale.     

Zircon U–Pb ages from tuff beds of the upper Mesozoic Tetori Group in the Shokawa district,Gifu Prefecture,central Japan†

Abstract The upper Mesozoic Tetori Group contains numerous fossils of plants and marine and non‐marine animals. The group has the potential to provide key information to improve our understanding of the Middle Jurassic to Early Cretaceous biota of East Asia. However, the depositional age of the Tetori Group remains uncertain, and without good age constraints, accurate correlation with other areas is very difficult. As a first step in obtaining reliable ages for the formations within the Tetori Group, we used laser ablation‐inductively coupled plasma–mass spectrometry to measure the U–Pb ages of zircons collected from tuff beds in the Shokawa district, Takayama City, Gifu Prefecture, central Japan. The youngest reliable U–Pb ages from the tuff beds of the Ushimaru, Mitarai and Okurodani Formations are 130.2 ± 1.7, 129.8 ± 1.0 and 117.5 ± 0.7 Ma, respectively (errors represent 2 SE). These results indicate that the entire Tetori Group in the Shokawa district, which was previously believed to be correlated to the Upper Jurassic to Lower Cretaceous, is in fact correlated to the Lower Cretaceous. The maximum ages of the Ushimaru, Mitarai and Okurodani Formations are late Hauterivian to Barremian, late Hauterivian to Barremian and Barremian to Aptian, respectively.     

The impact of the South–North Water Transfer Project (CTP)'s central route on groundwater table in the Hai River basin,North China

The central route of the South–North Water Transfer Project (CTP) is designed to divert approximately 9.5 billion m³ of water per year from the Han River, a major tributary of the Yangtze River, to the Hai River basin in the north China. The main purpose of this study is to assess the impact of CTP on groundwater table in the Hai River basin. Our study features a large‐scale distributed hydrological model that couples a physically based groundwater module, which is sub‐basin‐based, with a conceptual surface water module, which is grid‐based. There are several grids in each sub‐basin and water exchange among grid that are considered. Our model couples surface water module and groundwater module and calculates human water use at the same time. The simulation results indicate that even with the water supply by CTP, the groundwater table will continue to decline in the Hai River basin. However, the CTP water can evidently reduce the decline rate, helping alleviate groundwater overexploitation in Hai River region. Copyright © 2013 John Wiley & Sons, Ltd.