1981-2017年砚瓦川流域蒸发量变化特征研究

利用砚瓦川流域1981-2017年蒸发量实测数据，运用数理统计、线性回归分析、Man-Kendall检验等方法分析研究砚瓦川流域多年蒸发量变化特征。结果表明，（1）砚瓦川流域37年蒸发量变化总体呈下降趋势，其平均减少速率为4.75mm，2006年是减少突变年。（2）砚瓦川流域37年年平均蒸发量为1182.23mm，80年代的年均蒸发量高于平均值。（3）砚瓦川流域春季蒸发量波动幅度最大，秋季次之，冬季蒸发量波动幅度最小，夏季蒸发量最大，约占全年蒸发量的42.36%。（4）砚瓦川流域月平均蒸发量最大的为6月，最小的为12月。（5）砚瓦川37年降雨量和蒸发量均在减小，但降雨量的减小速率略大于蒸发量的减小速率。     

Assessment of insurance coverage and claims in rainfall related risks in processing tomato in Western Spain

An extension of guarantees related to rainfall-related risks in the insurance of processing tomato crops has been accompanied with a large increase in claims in Western Spain, suggesting that damages may have been underestimated in previous years. A database was built by linking agricultural insurance records, meteorological data from local weather stations, and topographic data. The risk of rainfall-related damages in processing tomato in the Extremenian Guadiana river basin (W Spain) was studied using a logistic model. Risks during the growth of the crop and at harvesting were modelled separately. First, the risk related to rainfall was modelled as a function of meteorological, terrain and management variables. The resulting models were used to identify the variables responsible for rainfall-related damages, with a view to assess the potential impact of extending insurance coverage, and to develop an index to express the suitability of the cropping system for insurance. The analyses reveal that damages at different stages of crop development correspond to different hazards. The geographic dependence of the risk influences the scale at which the model might have validity, which together with the year dependency, the possibility of implementing index based insurances is questioned.     

Effect of time resolution of rainfall measurements on the erosivity factor in the USLE in China

Rainfall erosivity, one of the factors in the Universal Soil Loss Equation, quantifies the effect of rainfall and runoff on soil erosion. High-resolution data are required to compute rainfall erosivity, but are not widely available in many parts of the world. As the temporal resolution of rainfall measurement decreases, computed rainfall erosivity decreases. The objective of the paper is to derive a series of conversion factors as a function of the time interval to compute rainfall erosivity so that the R factor computed using data at different time intervals could be converted to that computed using 1-min data. Rainfall data at 1-min intervals from 62 stations over China were collected to first compute the ‘true’ R factor values. Underestimation of the R factor was systematically evaluated using data aggregated at 5, 6, 10, 15, 20, 30, and 60-min to develop conversion factors for the R factor and the 1-in-10-year storm EI₃₀ values. Compared with true values, the relative error in R factor using data at fixed intervals of ≤10min was <10% for at least 44 out of 62 stations. Errors increased rapidly when the time interval of the rainfall data exceeded 15 min. Relative errors were >10% using 15-min data for 66.1% of stations and >20% using 30-min data for 61.3% of stations. The conversion factors for the R factor, ranging from 1.051 to 1.871 for 5 to 60-min data, are higher than those for the 1-in-10-years storm EI₃₀, ranging from 1.034 to 1.489 for the 62 stations.     

Determinants of groundnut rosette virus disease occurrence in Uganda

Groundnut rosette virus disease (GRVD) is the major constraint to groundnut (Arachis hypogaea) production in Uganda. It is principally transmitted by the groundnut aphid (Aphis craccivora Koch). The disease is known to cause total crop failure in cases where susceptible varieties are used. During any particular season, GRVD displays variations in incidence and severity in different agro-ecologies within the country, but the reasons for the varying disease patterns remain unclear. This study was aimed at establishing the factors influencing the occurrence of GRVD in Uganda. Trials were established for three seasons in four groundnut growing locations situated in different agro-ecologies in Uganda. Four groundnut genotypes were used as treatments in a randomized complete block design with four replications. Disease progress and aphid populations were assessed at 4, 8 and 12 weeks after planting. Data on environmental factors; particularly rainfall, temperature and wind speed were obtained from standard meteorological stations located at/near the study sites. Soil samples and yield data were also obtained in each season. The study revealed that disease incidence; severity and groundnut yields were significantly affected by season, location and genotype. The same applied to their three way interactions. Levels of disease infection were found to be majorly influenced by rainfall and wind speed. Disease incidence and severity were generally higher in conditions with less rainfall and low wind speeds. The Pearson's two tailed correlation between total rainfall and disease incidence for all trial sites was negative and highly significant (r = −0.280, P ≤ 0.01). The same was true for wind speed and disease incidence (r = −0.476, P ≤ 0.01). However, there was no conclusive trend between temperature and disease incidence with the Pearson's two tailed correlation showing significantly positive and negative trends depending on location.     

1960～2010年宜良县降雨量和蒸发量变化特征分析

利用宜良县1960～2010年的年降水量和小型蒸发量资料,采用线性趋势、干燥度等统计学方法,分析近51年宜良县降雨量和蒸发量的变化特征.结果表明,1960～ 2010年宜良县降雨量和蒸发量均在逐年减小,特别是21世纪以来降雨量和蒸发量均减少,可利用水资源较少.宜良县降雨主要集中在5～10月,蒸发主要集中在3～9月,其中3～5月降雨量较少,而蒸发对水的消耗比较明显,气候比较干燥,容易发生春旱;10 ～11月蒸发对水的消耗比较小,而这个阶段降水也比较少,也容易发生秋旱.     

Runoff estimation in southern Brazil based on Smith's modified model and the Curve Number method

The objective of this work was to measure and model the runoff for different soils classes at different rainfall intensities (30, 60 and 120 mm h⁻¹) in Southern Brazil. A portable rainfall simulator with multiple nozzles was used to simulate these rainfall intensities. For each soil, the initial time and runoff rate, rainfall characteristics (total, duration and intensities), surface slope, crop residue amount and cover percentage, soil densities (bulk and particle), soil porosity (bulk, macro and micro), textural fractions (clay, silt and sand), and the initial and saturated soil water content were measured. The runoff measured was compared to Smith's modified and Curve Number (USDA-SCS) models. The cumulative runoff losses were 67, 45 and 27% of the total rainfall, for a Rhodic Paleudalf, Typic Quartzipsamment and Rhodic Hapludox, respectively. An inverse relationship was observed between initial runoff and the runoff rate, independently of the soil surface and rainfall conditions. Increasing rainfall intensity decreased the time to runoff and increased runoff rate. The Smith's modified model overestimated the cumulative runoff by about 4%. The Smith's modified model presented a better estimate for both higher and lower rainfall intensities (120 and 30 mm h⁻¹). The SCS Curve Number model overestimated the cumulative runoff by about 34%. This large overestimate is probably due to that the model did not take into account the soil tillage system used in the field by farmers, particularly for irrigated conditions. The combination of high porosity, low bulk density and presence of crop residue on soil surface decreased runoff losses, independently of the soil texture class. Smith's modified model better estimated the surface runoff for soil with a high soil water content, and it was considered satisfactory for Southern Brazil runoff estimations. The SCS Curve Number model overestimated the cumulative runoff and its use needs adjustments particularly for no-tillage management system.     

Phosphorus dynamics in tile-drain flow during storms in the US Midwest

Excess phosphorus (P) in freshwater systems has been associated with eutrophication in agro-ecosystems of the US Midwest and elsewhere. A better understanding of processes regulating both soluble reactive phosphorus (SRP) and total phosphorus (TP) exports to tile-drains is therefore critical to minimize P losses to streams while maintaining crop yield. This paper investigates SRP and TP dynamics at a high temporal resolution during four spring storms in two tile-drains in the US Midwest. Depending on the storm, median concentrations varied between 0.006-0.025 mg/L for SRP and 0.057-0.176 mg/L for TP. For large storms (>6 cm bulk precipitation), for which macropore flow represented between 43 and 50% of total tile-drain flow, SRP transport to tile-drains was primarily regulated by macropore flow. For smaller tile-flow generating events (<3 cm bulk precipitation), for which macropore flow only accounted for 11-17% of total tile-drain flow, SRP transport was primarily regulated by matrix flow. Total P transport to tile-drains was primarily regulated by macropore flow regardless of the storm. Soluble reactive P (0.01-1.83 mg m⁻²/storm) and TP (0.10-8.64 mg m⁻²/storm) export rates were extremely variable and positively significantly correlated to both mean discharge and bulk precipitation. Soluble reactive P accounted for 9.9-15.5% of TP fluxes for small tile-flow generating events (<3 cm bulk precipitation) and for 16.2-22.0% of TP fluxes for large precipitation events (>6 cm bulk precipitation). Although significant variations in tile-flow response to precipitation were observed, no significant differences in SRP and TP concentrations were observed between adjacent tile-drains. Results stress the dominance of particulate P and the importance of macropore flow in P transport to tile-drains in the US Midwest. Although only spring storms are investigated, this study brings critical insight into P dynamics in tile-drains at a critical time of the year for water quality management.     

华北土石山区模拟降雨下土壤溅蚀研究

采取野外模拟降雨试验,研究了降雨强度、降雨动能以及降雨历时对溅蚀量的影响规律,分析了溅蚀土粒的距离、方位的分布特征,以及溅蚀土粒的粒径组成规律。研究结果表明:雨滴击溅过程中,在不同强度的降雨作用下,下坡方向产生的溅蚀量最大,上坡方向产生的溅蚀量最小。溅蚀总搬运量与溅蚀净搬运量均与降雨强度呈正相关。溅蚀量与降雨强度呈指数函数关系,与降雨动能呈现线性函数关系。溅蚀率与降雨历时呈现指数函数关系。溅蚀土粒主要分布在0~10 cm,占溅蚀总搬运量的45.40%~57.75%,在50~60 cm内的溅蚀量所占比例不高于1.75%。溅蚀量与溅蚀距离呈负指数函数关系。溅蚀土粒径小于等于2 mm,溅蚀土粒中细砂粒和粗粉粒百分比与原状土壤较为接近,粗砂粒百分比远低于原状土壤,而粘粒百分比高于原状土壤,粉粒百分比低于原状土壤。溅蚀土粒中细砂粒(0.05~0.2 mm)最易于被溅蚀,而小粒径(小于0.002 mm)和大粒径(大于0.2 mm)土壤颗粒不易被溅蚀。当降雨强度足够大时,对于同种特征的土壤,溅蚀土粒存在稳定的粒径组成。当降雨强度保持不变时,溅蚀平均粒径随溅蚀距离的增加而变小。溅蚀距离在0~30 cm,溅蚀平均粒径的变化率较大;随溅蚀距离的不断增加,溅蚀平均粒径的变化率较小。     

降雨强度和坡度对细沟形态特征的综合影响

细沟的形态特征研究可揭示坡面侵蚀发生机理,且细沟形态对坡面径流和侵蚀有重要影响;而现有研究仅用细沟密度和细沟宽深比等指标来表征细沟形态,不能全面准确地反映细沟的形态特征。为此基于模拟降雨试验,研究降雨强度和坡度对黄土坡面细沟侵蚀和细沟形态特征的综合影响。试验处理包括3种黄土高原有代表性的侵蚀性降雨(50、75、100 mm/h)和3个细沟侵蚀发生最常见的坡度(10°、15°、20°)。试验结果表明,坡面侵蚀速率和细沟侵蚀速率均随着降雨强度和坡度的增加呈幂函数增加。试验条件下,细沟倾斜度介于16°~20°之间,随着降雨强度的增加而增大,随着坡度的增加而减小;细沟密度、细沟割裂度和细沟复杂度分别为0.74~1.95 m/m2、0.08~0.17和1.09~1.38,三者皆随降雨强度和坡度的增加而增大;细沟宽深比为1.93~2.35,随着降雨强度和坡度的增加而减小。通过相关分析发现,细沟割裂度是评价细沟侵蚀和细沟形态的最优指标;研究降雨强度对细沟形态的影响时,建议优先选用细沟割裂度、细沟复杂度和细沟倾斜度指标;分析坡度对细沟形态的影响时,除选取细沟割裂度外,建议优先选用细沟密度和细沟宽深比指标。细沟横断面主要呈"V形",随着降雨强度和坡度的增加,径流紊动性增强,细沟横断面变化趋于不规则,说明细沟横断面变化可以反映径流的变化特征,从而揭示细沟侵蚀发生机理。     

Incorporation of ridge and furrow method of rainfall harvesting with mulching for crop production under semiarid conditions

A plastic-covered ridge and furrow rainfall harvesting (PRFRH) system combined with mulches was designed to increase water availability to crops for improving and stabilizing agricultural production in the semiarid Loess region of northwest China. The system was built by shaping the soil surface with alternate ridges and furrows along the contour. The plastic-covered ridges served as a rainfall harvesting zone and furrows as a planting zone. Some materials were also used to mulch the furrows to increase the effectiveness of the harvested water. This system can make better utilization of light rain by harvesting rainwater through the plastic-covered ridge. The field experiment (using corn as an indicator crop) showed that grain yields in the PRFRH system with mulches in 1998 and 1999 were significantly higher than the controls, with an increase of 4010–5297 kg per ha (108–143%). In most treatments, the water use efficiencies (WUE) were in excess of 2.0 kg m⁻³. The WUE values of corn in this system were 1.9 times greater than the controls in 1998 and 1.4 times greater than the controls in 1999. The plastic-covered ridge led to a yield increase of 3430 kg per ha (92%) in 1998 and of 1126 kg per ha (21%) in 1999 compared with the uncovered ridge. On average, the additional mulches in the furrow brought about a yield increase of 8–25%. Based on the results of this study and other researches, this technique can increase corn grain yield by 60–95% in drought and average years, 70–90% in wet years, and 20–30% in very wet years. The PRFRH system had the potential to increase crop yield and produced greater economic benefit, therefore it could be used in regions dominated by light rainfall of low intensity where crops generally fail due to water stress.