Towards Development of Eco-Agriculture of Rainwater-Harvesting for Supplemental Irrigation in the Semi-Arid Loess Plateau of China

The semi-arid Loess Plateau is a central zone of Chinese rain-fed farming. Drought and soil erosion are the two major obstacles to restrict economic development in this semi-arid Loess Plateau. The traditional conservation agriculture and runoff agriculture have been developed for several decades, which have reduced water and soil loss and improved rainwater utilization efficiency to a certain extent. However, its regulative role in rainwater is very much limited, and problems of agriculture production, such as severe seasonal drought and water shortage, low agriculture productivity, fragile ecological environment, and low yield-invest ratio, are still going on. Supplemental irrigation of harvested rainwater is an important form of rainfall regulation and utilization on the basis of sophisticated technologies and theories of conservation agriculture and runoff agriculture, which not only promotes fulfilling rainfall harvesting in spatial location like the conservation agriculture and runoff agriculture measure but also gets at true rainfall harvesting in time distribution by principle of superposition and also decreases invalid evaporation for rainfall runoff. Agriculture productivity will be highly increased by using rainwater harvesting for supplemental irrigation. It not only brings about the integration of ecological reconstruction with economic development, but also provides a new approach to the agriculture sustainable development and overcomes two of the biggest obstacles (drought and soil erosion). It is suggested that this technology will become a strategic measure and comprehensive development model in semi-arid Loess Plateau of China.     

SCS模型在紫色土坡地降雨径流量估算中的运用

为了合理利用紫色土流域的水土资源,对紫色土坡地的降雨产生的径流量进行模拟,为农田非点源污染物输出模拟提供科学依据。此次试验地位于四川盆地中部,独特的紫色土资源与亚热带气候的最佳组合成为四川农业的主体区域,运用SCS模型计算试验小区在2005年的三场降雨产生的径流量,通过校正Ia和CN参数,小区计算值和实测值的误差分别为6.46%,10.22%和8.40%,得到了可信度较高的结果,同时说明了SCS模型在估算紫色土流域径流量的可行性。     

Influence of a polyacrylamide soil conditioner on runoff generation and soil erosion: Field tests in Baringo District,Kenya

Following promising laboratory results the effect of low concentration applications of a polyacrylamide soil conditioner SEPARAN AP30 on soil properties was tested under field conditions in a severely degraded semi-arid region in northern Kenya. Tests of conditioner performance on tilled and undisturbed soils were carried out under simulated rainfall on crusting Eutric or Calcaric Fluvisols at two sites on alluviolacustrine flats adjacent to Lake Baringo. Tests were carried out in two series separated by up to six weeks of sunshine and natural rainfall, to determine the longevity and residual effects of conditioner application.Runoff generation and soil loss were significantly reduced on all runoff plots during the first rainfall simulation, but the most dramatic results occurred when conditioner application was combined with raking. This inhibited crust development and virtually eliminated runoff and soil loss. Under natural weathering, surface crust had developed on all plots before the second rainfall simulations. Some residual effects of the conditioner on infiltration rates were still noted, but the residual effect on soil loss was greatly diminished.The tests indicate that low concentration applications of SEPARAN are not useful on undisturbed soils, but can provide useful temporary reductions in sheet and rillwash hazard when combined with tillage and could be effectively combined with grass re-seeding for more permanent reclamation.     

坡度对云南红壤径流中磷素浓度的影响研究

水体富营养化的发生与农田土壤中磷的淋失有密切的关系。采用模拟降雨试验研究了土壤坡度对地表径流和亚地表径流中磷素浓度的影响。结果表明：在0°—10°范围内,地表径流中总磷、水溶性磷和颗粒态磷浓度和亚地表径流中水溶性磷浓度都随土壤坡度的增加而增加。亚地表径流中总磷和颗粒态磷在坡度为15°时均有一定程度的下降,其下降机理将做下一步分析研究。     

Characterization of rainfall - microrelief interactions with runoff using parameters derived from digital elevation models (DEMs)

The main objective of this study was to investigate how the interactions between rainfall energy and microrelief affect soil surface sealing and runoff. Furthermore, several roughness indices and geostatistical procedures were tested for their ability to characterize microrelief.Runoff boxes filled with soil from the plough layer of a silty Luvisol were subjected to simulated rainfall. Two types of microrelief (rough and fine) were tested at two rainfall intensities (30 and 60 mm/h). A photogrammetric technique was used to develop digital elevation models (DEMs) of the soil surface before and after rainfall with a resolution in height of 0.2 mm and a grid spacing of 2 mm.The random roughness coefficient according to Currence & Lovely (1970) was found to be sensitive to surface microrelief variations. Semivariograms of the data indicated that big clods were the main elements determining microrelief and the ratio of total surface are to map area. The observed variations in runoff as a function of microrelief were best explained by rainfall energy per total surface area and by the relative contribution of the effective normal component of kinetic energy with respect to the impact angle of raindrops. Microdepression storage was only 0.6 mm or less and was found to be negligible in terms of runoff.     

安徽省沿淮大豆种植区氮磷流失特征研究

为了探明沿淮地区大豆农民常规施肥种植过程中的氮磷流失情况,采用径流池法,通过2008—2012年野外径流小区试验,研究沿淮大豆种植区大豆生长季氮磷流失特征。5年监测结果表明:大豆种植季处于沿淮地区全年降雨旺盛时期,降雨量占全年降雨量的45.4%~73.27%;大豆生产季农田产流量表现为不施肥空白处理常规处理,不施肥空白处理大豆生长季径流量和产流系数分别为173.293~34.639 mm和8.27%~33.68%,常规施肥处理大豆生长季径流量和产流系数分别为175.366~30.347 mm和5.72%~34.08%;大豆种植生长季常规施肥处理总氮流失量为1.58~14.93 kg/hm2,总氮流失率为0.44%~5.66%,硝态氮流失比例为总氮的40.63%~64.59%,铵态氮流失比例为3.66%~18.16%;大豆种植生长季常规施肥处理总磷流失量为0.033~0.56 kg/hm2,常规施肥处理总磷流失率为0.17%~0.27%,可溶性磷流失比例为总磷的31.08%~53.31%。     

滇池流域农田土壤氮污染负荷影响因素研究

采取模拟试验的方法,研究了在人工降雨和自然降雨条件下,坡度、土壤质地、地表覆盖状况以及施肥方式对坡地农田径流中氮素污染负荷的影响。结果表明：随着坡度的增加,农田土壤径流中氮的浓度和氮的输出量都增加;在人工模拟降雨和自然降雨条件下,土壤径流中氮的浓度变化趋势相同,都随着质地的变粗而减少;和裸地相比,种植小麦能明显减少土壤径流中氮的浓度和输出量,氮的流失量减少范围在11.80~238.46kg/hm2之间;相同施肥量条件下,面施氮肥时土壤径流中氮的浓度和输出量比穴施时明显增加。     

Cropping system effects of maize on infiltration,runoff and erosion on loess soils in South-Limbourg (The Netherlands): A comparison of two rainfall events

Two natural rainfall events are compared to evaluate the effects of three cropping systems of silage maize on soil moisture content, infiltration, runoff and erosion. Both rainfall events took place in early summer. One was a low intensity event with 27.6 mm of rain in 9 hours, and the other a high intensity event with 33.4 mm in 42 minutes. Cropping systems were:

• 1.(I) a spring tilled system (conventional),
• 2.(II) an autumn and spring tilled system with summer barley as spring cover crop, and
• 3.(III) an autumn tilled system with winter rye as winter cover crop and direct drilling of silage maize.

During the low intensity event, soil moisture content of the top 5 cm rose to field capacity on all three cropping systems. No runoff was generated. During the high intensity event, soil moisture content rose to field capacity on the two spring tilled cropping systems but was only slightly raised in the direct drill system, in spite of 17.7 mm of infiltrated rain. Runoff coefficients of the high intensity event were 41.7% (conventional system), 14.9% (autumn and spring tilled system) and 47.0% (direct drill system). The direct drill system showed a severely slaked soil surface in early summer, caused by winter rain.The response to rainfall of soil moisture content is ascribed to:

• 1.(I) a predominance of matrix infiltration on all cropping systems during the low intensity event and on the spring tilled systems during the high intensity event, and
• 2.(II) a predominance of infiltration via continuous macropores, open to the surface (of biologic origin), by-passing the soil matrix, on the direct drill system during the high intensity event.

The presence of continuous, vertical macropores on the direct drill system explains its surprisingly high infiltration capacity, considering its strongly slaked appearance. The smooth soil surface of the direct drill cropping system may have delayed infiltration during the flooded stage of the high intensity event by not providing vent points for the escape of soil air. Soil loss from the direct drill system during the high intensity event was only 15.6% of that from the conventional system. This is ascribed to low detachment rates of soil material by drop impact and/or overland flow, due to the presence of winter rye remains and, especially, the relatively high soil surface shear strength of the direct drill cropping system in early summer.     

简单屋顶绿化的滞蓄特性

设计了模拟降雨与数据采集系统,研究了短时强降雨下简单屋顶绿化基质(配比：陶粒57.0%、草炭41.5%、保水剂1.5%)的降雨产流过程,基于37次模拟降雨实验,归纳了降雨产流的一般过程、规律和特性,分析了降雨强度、基质厚度和基质初始含水率对简单屋顶绿化滞流蓄水特性的影响。结果表明：基质厚度和基质初始含水率对简单屋顶绿化的蓄水特性有显著影响,基质初始含水率越低、基质厚度越厚时蓄水特性越佳。建立了产流时间数学模型,简单屋顶绿化降雨产流时间与降雨强度呈负相关,同时也受初始含水量和基质厚度影响。随着干湿循环次数增加,基质的厚度总体呈现下降趋势,储水性能逐渐下降,延迟产流时间逐渐缩短。     

黄土高原小杂粮降水生产潜力开发和增进的技术途径

在黄土高原,水资源已成为对粮食生产的主要制约因素。现阶段高原旱作农区农田降水利用效率仅为35%左右,研究表明在较为合理的生产条件用水效率可以达到70%~80%。在此,通过从提高种群的内在生产力、建设基本农田控制坡耕地水分的径流输出、抑制农田水分的无谓损耗、实施农田水分的空间富集、确立与降水分布相吻合的种植结构几方面阐述黄土高原小杂粮作物降水生产潜力开发和增进的技术途径。     

Calculating Annual Pollution Load in Urban Runoff

Sampling and monitoring of surface runoff in Bengbu urban area were carried out during rainy seasons in 2009, and 40 rainfall samples from 7 sampling sites were analyzed. Discharge processes of runoff pollutants during rain events and relationships of the processes with rainfall characters were discussed. Then some aspects were analyzed, such as city surface pollutants, land style and system of drains, etc. Finally annual total quantity of runoff pollution from Bengbu urban area was calculated based the method.     

Research on Influence of Frequency Flood on Water Environment Quality

Based on the two-dimensional hydrodynamic model,the two-dimensional water quality model is presented in this paper.According to the numerical simulation and analysis of water environment quality at different frequency floodwater,it concludes that the flood runoff is the first factor for the water environment quality,and points out that the water environment quality is better in low frequency flood than that in high frequency in respect of organic contamination,in addition,the concentration of heavy metal in high frequency flood tends to be increased greatly.     

Tidal and residual flows in the western Dutch Wadden Sea II: An analytical model to study the constant flow between connected tidal basins

In a one-dimensional analytical model the origin of constant flows between connected tidal basins, as well as the origin of the associated residual levels, is examined. Linearized shallow water equations are used to describe the propagation and damping of a tidal wave in schematized (uniform width and depth) connected basins. Analytical expressions are derived for the tidal stress terms, including the contribution of the non-linear bottom-friction term, which serve as the forcing functions in the equations for the mean field. It is shown that in a first approximation the residual levels in the tidal inlets, which give boundary conditions for the tidally-averaged equations, are dependent on the tidal velocities in the inlet because of a “Bernoulli effect”. The model shows that in general differences between the fluctuating water levels at the inlets influence the residual flow more than morphological differences between two connected basins. The tidally-driven mass transport in the western Dutch Wadden Sea, directed southwards from the Vlie basin towards the Marsdiep basin, can be explained from the larger water-level amplitude at the inlet of the Vlie basin.     

近35年甘肃庆阳黄土高原地带气候特征分析

通过研究全球气候变化下甘肃庆阳地区气候变化的特点,为黄土高原地带农业及经济的发展提供理论依据。研究利用庆阳市8 站近35 年的降水、气温、日照时数等气象资料,应用多种统计方法分析了庆阳黄土高原地带的区域气候特征及其变化规律。结果表明,甘肃庆阳黄土高原地带降水量季节分配不均,干湿季分明,强降水天气均出现在4—9 月。中部和东南部年降水量呈减少趋势,西北部呈增多趋势;气温差异性则表现为山壑地区比平原和川区冬天气温低,夏天气温高,年平均气温呈升高趋势,且升高趋势冬季贡献显著;年日平均日照时数西北部和中部呈增多趋势,东南部则呈明显减少趋势,4—8月为日照时数高值区,且夏季比冬季日照时数多出约1 h。     

近60年长江源区径流变化特征及趋势分析

为深入了解长江源径流的演变特征和变化趋势,笔者以长江源为研究区,采用集中度、集中期、线性倾向估计、Mann-Kendall突变检验、模比系数差积曲线,研究了长江源区径流的年内、年际、年代际趋势性变化,突变点检测和丰枯周期性。结果显示：长江源区1956—2012年径流量总体呈显著增加趋势,上游径流量年际变化较下游剧烈。长江源径流集中度主要集中在55%~85%,上游集中度高于下游。集中期主要分布在7月下旬—8月上旬且有推后趋势。沱沱河站径流主要受降水和冰雪融水补给,直门达站径流主要受降水、冰雪融水和地下水补给。21世纪以来,长江源径流进入丰水期,直门达站比多年平均增加19.3%,上游沱沱河站增加更为明显,达53.8%。沱沱河站年径流量突变点发生在2005年。直门达站年径流量突变点发生在1961、1968、2008年。1956—2012年沱沱河站有1个完整的丰平枯周期,直门达站有3个丰平枯周期。     

Chemical amelioration of surface crusting to reduce runoff and erosion on highly weathered soils

Because of the very low soil solution ionic strengths in highly weathered soils, clay particles can be readily dispersed under the impact of raindrops. The clay fraction of many soils is dispersible under the combined effects of mechanical disturbance and low electrolyte concentration. This clay dispersion results in fine particle segregation at the soil surface, with clay particles moving into and blocking soil pores resulting in the formation of a highly impervious crust which reduces infiltration. Because the clay is dispersed, the particles usually orient themselves in a laminar fashion as they settle. As a result, runoff is substantially increased, giving rise to soil erosion. The crusts formed in this manner often have very high strengths which prevent or substantially reduce crop emergence. The formation of such crusts can be prevented by the application of relatively low rates of by-product gypsum such as phosphogypsum on the soil surface which produces sufficient electrolyte in solution during raindrop impact to maintain the clay particles in a flocculated condition. The results of a number of experiments in which different soils were treated with phosphogypsum are discussed to illustrate the effects of electrolyte concentration, level of sodium and other factors on the formation of surface crusts and the consequent runoff and erosion. As a result of the application of phosphogypsum to the soil surface, a laminar orientation of clay particles at the surface is prevented, which allows a much greater proportion of the rainfall to enter the soil. Any crusts formed are thus much weaker and do not reduce seedling emergence. This type of crust formation can also be prevented by reducing raindrop impact through the use of mulches. This phenomenon occurs on many soils not normally considered to suffer from chemically-induced physical problems, which points to the importance of considering chemical as well as physical processes in the evaluation of potential runoff and erosion.     

水稻田磷径流流失特征初步研究

在自然降雨条件下,原位研究了广东省典型稻田地表径流氮磷输出的动态流失特征。结果表明,降雨量与产流量之量极显著正相关,但对P素流失量无明显影响;与未施肥对照(F0)相比,常规施肥(F)对P素流失没有显著影响（p > 0.05）,P素流失形态以颗粒态磷(pp)为主。     

Development and Application of Small Urban Watershed Storm Runoff Model in Mountain City

The small urban watershed storm runoff model of mountain city, which bases on the hydrological method and ArcEngine extension programming was developed aim at stimulating the flood situation, locating the flooding area, computing the subsiding time of flood, utilization and management of the stormwater through the rainfall data. The model was used in Panxi basin of Chongqing. The simulated situation showed that the Nash-Suttcliffe coefficient Ens is 0.56-0.76, the relatively error is 8.82%-11.8%. According to the parameter sensitivity analysis the most sensitivity parameters of the model are width of subcatchment, slope, manning coefficient and impermeable area rate. The model had analyzed the flow, full degree and number of overflowed wells to evaluate drainage capability of drainage system. Results showed that 0.52% of the drainage pipes were overload under one-year storm; compared with 5.86% and 8.20% under fifty-year storm and one-hundred-year storm respectively. By comparing the flow depth inside the wells with the placing depth the assessment results showed that 0.72% of the wells had spillover under one-hundred-year storm and 0.31% of the wells had spillover under one -year. Overall the model achieves effective management of storm runoff and assessment of the water drainage system capacity in mountainous city.     

紫色土壤氮素不同流失形式的比较研究

土壤氮素流失形式及其量化研究是农业小流域氮素管理及流失过程模拟的核心内容之一,以紫色土区3个具有不同地形和土地利用方式的典型农业小流域为研究对象,比较研究了区域土壤氮素在降雨侵蚀过程中流失的主要形式。结果表明,紫色土区土壤氮素以硝态氮为主要流失形式,其流失浓度一般占硝态氮和铵态氮总浓度的80%以上,农田利用为主流域的则高达90%以上。氮素流失的平均浓度因流域土地利用类型的差异而显著不同,农田的一般为(5.36±2.13) mg/l,而非农田利用的变化在1.70~3.15 mg/l之间。农田硝态氮的精确管理应作为减控流域土壤氮素非点源流失的关键措施。     

MIMYCS.Moisture,a process-based model of moisture content in developing maize kernels

Moisture content influences harvest timing and the consequent drying process and drying costs, and the development of spoilage fungi during pre- and post-harvest phases. Maize kernel development in the field can be partitioned into three phases: i) lag phase, ii) grain filling and maturation drying, and iii) post-maturity dry-down. A model simulating maize kernel moisture content during maturation can help either monitoring or foreseen maize kernel humidity during the harvest period. Also, it would be useful in simulation studies via crop models to estimate the infield feasibility of harvest but also the interaction with diseases responsible for mycotoxin production, against weather scenarios.A process-based model was developed, called MIMYCS.Moisture. When the hybrids were analyzed all together, MIMYCS.Moisture showed a good general predictive capability with an average error in moisture estimation of ±3.28% moisture (considering the root mean square error – RMSE). The model efficiency (EF) was positive (0.85) and the model was able to explain the 89.7% of variation. When the two sub-models were analyzed separately, the RMSE remained approximately at the same level of the general model, while the other indicators changed revealing the different characteristics of the two models. The developmental moisture sub-model has a slight tendency to overestimate, while the dry-down sub-model tended to underestimate final moisture content.However, when the model was analyzed separately for each hybrid, both calibration and validation results suggested that more data are needed to improve the model likely with respect to kernel characteristics of hybrids. Finally, the equilibrium moisture content equation used, taken from industrial drying models, might not be adequate for simulating the field conditions where temperature is well below the one in dryers and environmental air humidity may vary considerably across sites and harvest periods.