Development of an appropriate procedure for estimation of RUSLE EI30 index and preparation of erosivity maps for Pulau Penang in Peninsular Malaysia

Pluviographic data at 15 min interval from 6 stations in Pulau Penang of Peninsular Malaysia were used to compute rainfall erosivity factor (R) for the revised universal soil loss equation (RUSLE). Three different modelling procedures were applied for the estimation of monthly rainfall erosivity (EI₃₀) values. While storm rainfall (P) and duration (D) data were used in the first approach, the second approach used monthly rainfall for days with rainfall ≥ 10 mm (rain₁₀) and monthly number of days with rainfall ≥ 10 (days₁₀). The third approach however used the Fournier index as the independent variable. Based on the root mean squared error (RMSE) and the percentage error (PE) criteria, models developed using the Fournier index approach was adjudged the best with an average PE value of 0.92 and an average RMSE value of 164.6. Further, this approach was extended to the development of a regional model. Using data from additional sixteen stations and the Fournier index based regional model, EI₃₀ values were computed for each month. ArcView GIS was used to generate monthly maps of EI₃₀ values and also annual rainfall erosivity (R). The rainfall erosivity factor (R) in the region was estimated to vary from 9000 to 14,000 MJ mm ha^− 1 h^− 1 year^− 1.     

Permanence of soil surface crusts on abandoned farmland in the Central Ebro Basin/Spain

Surface crusts are frequently found on fallow land in the semi-arid Ebro Basin (Spain) and are an important factor in land degradation. Soil surface sealing leads to a decrease in infiltration rates and a consequent increase in runoff, thereby accelerating sheet wash and rill erosion. Thin sections were used to analyse the development and structures of the different crusts found across the ridge/furrow field pattern. Rainfall simulations experiments and infiltration measurements show the runoff generation and the soil erosion rates on the crusts. The spatial distribution of crusts was documented using large-scale aerial photographs, taken from a remote-controlled hot air blimp.     

Phosphorus and iron erosion from non-vegetated sites in a post-mining landscape,Lusatia, Germany: Impact on aborning mining lakes

Particulate phosphorus (P) can be transported via soil erosion in overland flow to waters, where it provides a long-term source of P for aquatic biota, and can accelerate freshwater eutrophication. Hence, knowledge of P sources is important for good environmental management. However, data on P, and related Fe, losses from various structures of a post-mining landscape are lacking. A year-long monitoring, and ten short rainfall simulations on plot scale, at ridges and rills and a combination of them, revealed high erosion from bare lignite mining dumps at Schlabendorf-North, Lusatia, Germany. The mean annual soil erosion rate from the year-long monitoring site was 18 × 10⁶ kg km^− 2 yr^− 1, corresponding to 0.034 g m^− 2 min^− 1. The erosion rates were lowest at rill plots (1.9–4.4 g m^− 2 min^− 1), intermediate at ridge plots (14.3–37.1 g m^− 2 min^− 1), and highest at a combined rill and ridge plot (48.7–63.4 g m^− 2 min^− 1). These differences in extent were due to small scale differences in morphology and extreme water repellency. The hydrophobicity leads to very low infiltration, thus generating surface runoff even at low rainfall intensities. Loss rates of P and Fe, as deduced from the year-long erosion rate, were 470–650 kg km^− 2 yr^− 1, and 37.9 × 10³–71 × 10³ kg km^− 2 yr^− 1 respectively. However, these P inputs from lignite mining dump erosion, consisting of P-poor (17–90 μg g^− 1) tertiary spoil materials, into aborning mining lakes, are negligible since they are accompanied by high Fe inputs, which favour an efficient P co-precipitation in the water column.     

Seasonal variability of runoff and soil loss on forest road backslopes under simulated rainfall

Runoff and soil loss from forest road backslopes is a serious problem in Mediterranean areas. Surface runoff and sediment production on backslopes of forest roads in Los Alcornocales Natural Park (southern Spain) has been studied in this paper using a simple portable rainfall simulator at an intensity of 90 mm h^− 1. One hundred rainfall simulations were performed on bare and vegetated road backslopes during summer and winter in order to study seasonal differences. Runoff coefficients and soil loss rates were lower on the vegetated plots than on the bare ones. Runoff coefficients increased 1.7 (bare backslopes) and 3.1 times (vegetated backslopes) from summer to winter. Preserving the vegetation cover over 20% is recommended for keeping soil loss rates under low levels, especially during winter.     

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.     

Interaction between the effects of evaporation rate and amount of simulated rainfall on development of the free-living stages of Haemonchus contortus

A factorial experiment (3 x 4 x 2 x 3) was conducted in programmable incubators to investigate interaction between the effects of rainfall amount, rainfall distribution and evaporation rate on development of Haemonchus contortus to L3. Sheep faeces containing H. contortus eggs were incubated on sterilised soil under variable temperatures typical of summer in the Northern Tablelands of NSW, Australia. Simulated rainfall was applied in 1 of 3 amounts (12, 24 or 32 mm) and 4 distributions (a single event on the day after deposition, or the same total amount split in 2, 3 or 4 equal events over 2, 3 or 4 days, respectively). Samples were incubated at either a Low or High rate of evaporation (Low: 2.1-3.4 mm/day and High: 3.8-6.1 mm/day), and faeces and soil were destructively sampled at 4, 7 and 14 days post-deposition. Recovery of L3 from the soil (extra-pellet L3) increased over time (up to 0.52% at day 14) and with each increment of rainfall (12 mm: <0.01%; 24 mm: 0.10%; 32 mm: 0.45%) but was reduced under the High evaporation rate (0.01%) compared with the Low evaporation rate (0.31%). All rainfall amounts yielded significantly different recoveries of L3 under Low evaporation rates but there was no difference between the 12 and 24 mm treatments under the High evaporation rate. The distribution of simulated rainfall did not significantly affect recovery of infective larvae. Faecal moisture content was positively associated with L3 recovery, as was the ratio of cumulative precipitation and cumulative evaporation (P/E), particularly when measured in the first 4 days post-deposition. The results show that evaporation rate plays a significant role in regulating the influence of rainfall amount on the success of L3 transmission.     

Yield-rainfall relationships in cereal cropping systems in the Ebro river valley of Spain

Wheat and barley yields from three farms in the Ebro river valley are shown to be strongly dependent on seasonal rainfall, particularly that during November-January and March-May of the cropping season. In the driest farm, in Monegrillo, Zaragoza province (seasonal rainfall, 251 mm), yields increased by c. 5.9 (wheat) and 9.4 (barley) kg ha⁻¹ per mm of extra rain during the entire cropping season, taken as October-May inclusive. The other farms, at El Canós and Selvanera in Lleida province, had seasonal rainfalls of 364 and 334 mm, and yields of barley increased by 4.3 and 9.0 kg ha⁻¹, respectively, per mm of extra rain in the cropping season, taken as September to May inclusive.

In Monegrillo, cereals are grown in a cereal-fallow rotation. Normal fallowing (duration 17 months) compared to minimum fallowing (5 months) increased the calculated water content of the top 100 cm of the dominant soils by 19 mm. This extra water was estimated to benefit yield by 7.0% (wheat) and 6.2% (barley), raising the average yields of crops greater than 300 kg ha⁻¹ to 1222 and 1522 kg ha⁻¹, respectively. Agronomic practices in Monegrillo during the fallow should focus on means of increasing the proportion of the rain stored in the profile during the fallow. At all three locations, decreasing water evaporation from the soil during the cropping season would likely benefit yield.     

TRMM/GPM和Stage IV降水产品在小流域水文模拟效用评估

以地面观测降水作为参照,在美国俄克拉荷马州Little Washita River流域,对比分析了TRMM 3B42 V7,GPM-IMERG卫星降水和Stage IV雷达降水的精度,并用这3种降水产品驱动CREST分布式水文模型,评估了其水文模拟效用.研究表明:3种降水产品与地面降水的相关系数均大于0.5,通过了0.05置信水平检验;GPM-IMERG和TRMM3B42 V7卫星降水对无雨和微雨存在低估,对大雨和暴雨存在高估;总体上,Stage IV降水精度最好,其次GPM降水精度优于TRMM 3B42 V7.在水文模拟效用评估中,设定相同率定期,分别使用3种降水产品率定CREST模型参数,得到率定参数集后,在相同验证期对流域日径流过程进行模拟.对比结果表明:Stage IV雷达降水在小流域水文模拟中效果最好,GPM-IMERG次之,TRMM 3B42 V7模拟效果不理想.     

湖南省大围山杉木新造幼林水土流失的研究

本文对杉木新造林地进行了水土保持观测,取得了研究数据和科学结论,以指导杉木造林。１径流场地点基本情况径流场地位于湖南省浏阳县张访林场,地处幕阜山系大围山南麓。多年平均降水量１５５２３ｍｍ,历年日最大降水量为２７６１ｍｍ（１９６５０７０６）,年...