Key physical characteristics used to assess water harvesting suitability     

《Physics and Chemistry of the Earth》2013

Water harvesting (WH) techniques, which aim to increase water availability to crops, have long been used in arid and semi-arid areas to decrease the risk of reduced yields and crop failures due to dry spells. The landscape conditions dictate the type of WH system that can be implemented as well as the quantity and quality of water that will be collected. The measurement and understanding of how these landscape characteristics influence the hydrological function of WH systems is important and essential for further studies which seek to understand and enhance efficiency, extend uptake and model the impacts of WH within a catchment. However, commonly used guidelines often only prescribe optimal conditions for WH which results in many sites which may be suitable being over looked. Various statistical analyses was performed on 28 WH sites gathered from the available literature to try and identify whether the landscape conditions under which WH is currently taking place differs to the recommended guidelines. The results show that WH is taking place under a much broader range of conditions than those recommended by the guidelines. The recommendations for minimum and maximum slope in particular are too restrictive, with examples of successful WH taking place on slopes much steeper than the stipulated guidelines. A new set of guidelines are suggested, which take into account not only optimal conditions but also a range of suitable conditions on either side of the optimal range.  相似文献   

Analysis of suspended sediment yields after low impact forest harvesting     

Norifumi Hotta  Toshiya Kayama  Masakazu Suzuki 《水文研究》2007,21(26):3565-3575

Disturbances to forest catchments have profound effects on the environment of headwater streams and have an impact on suspended sediment (SS) management. Forest harvesting is a dominant factor in increasing SS yields. Road construction, skidder activity and ploughing associated with harvesting cause serious soil disturbance that results in SS increases. However, few studies have shown whether harvesting itself increases SS yields. This study examined how harvesting influenced SS yields in a steep forested area. During harvesting, soil surface disturbance was prevented as much as possible by using skyline logging treatments and piling branches and leaves at selected locations in the watershed. Using these methods, the representative SS rating curve did not change significantly after harvesting. The results also show that the characteristics of SS transport were related to the SS source area, and reveal that the riparian zone/stream bank was a dominant SS source area at the study site. Annual SS yields did not increase despite increasing annual water yields after harvesting. The limited water capacity of the soil at the study site likely led to only slight differences in pre‐ and post‐harvest water discharge from heavy rainfall events. Most SS was transported during heavy rainfall events, and increases in SS yields were not detected after harvesting. We concluded that it is possible to prevent post‐harvest SS increases by performing careful, low‐impact harvesting procedures. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Thermal regime of a headwater stream within a clear‐cut,coastal British Columbia,Canada     

R. D. Moore  P. Sutherland  T. Gomi  A. Dhakal 《水文研究》2005,19(13):2591-2608

This study examined the thermal regime of a headwater stream within a clear‐cut. The stream had a complex morphology dominated by step–pool features, many formed by sediment accumulation upstream of woody debris. Maximum daily temperatures increased up to 5 °C after logging, and were positively associated with maximum daily air temperature and negatively with discharge. Maximum daily temperatures generally increased with downstream distance through the cut block, but decreased with distance in two segments over distances of tens of metres, where the topography indicated relatively concentrated lateral inflow. Localized cool areas within a step–pool unit were associated with zones of concentrated upwelling. Bed temperatures tended to be higher and have greater ranges in areas of downwelling flow into the bed. Heat budget estimates were made using meteorological measurements over the water surface and a model of net radiation using canopy characteristics derived from fisheye photography. Heat exchange driven by hyporheic flow through the channel step was a cooling effect during daytime, with a magnitude up to approximately 25% that of net radiation during the period of maximum daytime warming. Heat budget calculations in these headwater streams are complicated by the heterogeneity of incident solar radiation and channel geometry, as well as uncertainty in estimating heat and water exchanges between the stream and the subsurface via hyporheic exchange and heat conduction. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Statistical analysis of flash flood events for designing water harvesting systems in an extremely arid environment     

Koichi Unami  Osama Mohawesh  Rasha M. Fadhil 《水文研究》2021,35(9):e14370

A water harvesting system for research purposes has been established in the Lisan Peninsula of the Dead Sea in the middle of the Jordan Rift Valley, where no authorized guideline is available for designing water harvesting systems. Rainfall and runoff, which occurred as flash floods, were observed at the downstream end of a gorge with a 1.12 km² barren catchment area from October 2014 through July 2019. Due to the extremely arid environment, runoff from the catchment is ephemeral, and the flash flood events can be clearly distinguishable from each other. Thirteen flash flood events with a total runoff volume of more than 100 m³ were successfully recorded during the five rainy seasons. Pearson and Spearman correlations between duration, total rainfall depths at two points, total runoff volume, maximum runoff discharge, bulk runoff coefficient, total variation in runoff discharge and maximum variation in runoff discharge of each flash flood event were examined, revealing no straightforward relationship between rainfall and runoff. The performance of the conventional SCS runoff curve number method was also deficient in reproducing any rainfall–runoff relationship. Therefore, probability distribution fitting was performed for each random variable, focusing on the lognormal distribution with three parameters and the generalized extreme value distribution. The maximum goodness-of-fit estimation turns out to be a more rational and efficient method in obtaining the parameter values of those probability distributions rather than the standard maximum likelihood estimation, which has known disadvantages. Results support the design of the water harvesting system and provide quantitative information for designing and operating similar systems in the future.  相似文献   

Relationships between recruits of abalone Haliotis midae,encrusting corallines and the sea urchin Parechinus angulosus     

《African Journal of Marine Science》2013,35(1):137-144

In kelp beds of the South-Western Cape, South Africa, a strong positive relationship exists between the sea urchin Parechinus angulosus and juveniles of the abalone Haliotis midae. Field surveys reported here revealed a positive, but weak, association between this urchin and H. midae recruits (i.e. individuals <3 mm shell length). Selectivity indices showed that recruits occurred exclusively on encrusting coralline algae and showed preferences for strongly textured corallines, rather than those with smooth texture. On smooth corallines, around 80% of recruits were under urchins, compared with about 25% on textured corallines, suggesting that any need for shelter beneath urchins is greatest on smooth surfaces.  相似文献   

Phylogeny of the Sepia officinalis species complex in the eastern Atlantic extends the known distribution of Sepia vermiculata across the Benguela upwelling region     

AJE Healey  NJ McKeown  WM Potts  CL de Beer  W Sauer  PW Shaw 《African Journal of Marine Science》2017,39(3):307-313

Accurate species identification and biogeographic characterisation are fundamental for appropriate management of expanding cephalopod fisheries. This study addresses this topic within the common cuttlefish Sepia officinalis species complex (S. officinalis, S. hierredda and S. vermiculata), with an emphasis on occurrence in African waters. Tissue samples from the currently presumed distributions of S. vermiculata and S. hierredda (from South Africa and Ghana/Angola, respectively) were sequenced for the cytochrome c oxidase subunit I (COI) and the cytochrome b (cytb) genes of the mitochondrial genome and then compared to existing S. officinalis sequences. Three highly divergent and reciprocally monophyletic clades, corresponding to S. officinalis, S. hierredda and S. vermiculata, were resolved, representing the first molecular confirmation of the distinct species status of S. hierredda and S. vermiculata. The sequences also revealed that, contrary to expectations based on presently published information, all samples from southern Angola were S. vermiculata. These results indicate that the range of S. vermiculata extends beyond the currently described northern limit and that S. hierredda and S. vermiculata may be indiscriminately harvested in Angolan waters. Finer-scale patterns within S. vermiculata phylogeography also indicate that the Benguela Current System and/or other environmental factors serve to isolate northern and southern stocks.  相似文献   

Quality issues in harvested rainwater in arid and semi-arid Loess Plateau of northern China   总被引：1，自引：0，他引：1  

Kun Zhu  Linus Zhang  William Hart  Mancang Liu  Hui Chen 《Journal of Arid Environments》2004,57(4):487-505

Loess soils cover vast areas in the arid and semi-arid regions of northern China. Due to the lack of reliable surface water and ground-water, rainwater harvesting has played a prominent role in farmers’ domestic usage and agricultural irrigation. An economical and valid type of water storage cistern with optimum design of components has been introduced to rural areas in the Loess Plateau. Different collection alternatives showed apparent variations in rainwater quality. By using different catchments, such as mortar roofs and cement-paved courtyards, compacted land or road surfaces, rainwater can be effectively collected for storage in cisterns. This study focused mainly on the quality of rainwater harvested from the different catchment systems and stored for different periods of time. By analysis of the water samples stored in these cisterns, it was evident that rainwater quality could be improved significantly by self-purification during the storage. With emphasis on rainwater quality affected by the different catchment systems, it was found that the measured inorganic compounds in the rainwater harvested from roof-yard catchment systems generally matched the WHO standards for drinking water, while the concentrations of some inorganic compounds in the rainwater collected from land and road surfaces appeared to be higher than the guideline values for drinking water, but generally not beyond the maximum permissible concentrations. However, Fecal Coliform, which is an important bacteriological parameter for the three catchment systems, exceeded the limits of drinking water to a greater extend. Trace amounts of 55 organic pollutants were identified, including aliphatic hydrocarbons, aromatic compounds and phthalate esters, etc. The analytical results indicated that roof-yard catchments that included the “first flush” usually provided safe drinking water with low organic contents, even for rainwater collected immediately after rainfall. In contrast, rainwater harvested from road surfaces had poor quality with respect to the organic constituents, regardless of stored time.  相似文献   

Identification of rainwater harvesting sites using SCS-CN methodology,remote sensing and Geographical Information System techniques     

Tarun Kumar 《国际地球制图》2017,32(12):1367-1388

This study presents a method to identify potential sites for soil and water conservation techniques for the demarcation of suitable sites for artificial recharge of groundwater aquifers, in the study area. The run-off derived by the Soil Conservation Service Curve Number method is a function of run-off potential which can be expressed in terms of run-off coefficient. The augmentation of water resource is proposed by the construction of rainwater harvesting structures like check dam, percolation pond, farm pond and gully check dam. The site suitability for different water harvesting structures is determined by considering spatially varying parameters like slope, infiltration, run-off potential, landuse/land cover, stream order, soil texture, land capability class, hydrological soil group and micro-watershed area. The determined suitable site has been validated with existing recharge structures of the study area. Accuracy assessment of the suitable sites for recharge structures potential maps of the Bindra watershed is 82.60%.  相似文献   

Balanced harvesting: The institutional incompatibilities     

《Marine Policy》2016

Balanced harvesting is the name of a newly proposed approach to fishing which promises the extraction of high and sustainable fisheries yields while maintaining the structure of the ecosystem from which those yields could be obtained. This is to be achieved through exposing all components of ecosystems (from zooplankton to top predators, including seals, sea birds and marine mammals) to a fishing mortality proportional to their size-specific productivity. This study briefly analyses the incompatibility between balanced harvesting (and its implications) and the stated missions of two major organizations, FAO (which stresses the need of selective fishing in its Code of Conduct for Sustainable Fisheries) and IUCN (which maintains the Red List of Threatened Species), but which have issued reports or organized conferences promoting balanced harvesting. The study also demonstrates the incompatibility of balanced harvesting with the recently reformed Common Fisheries Policy of the European Union. While balanced harvesting appears partly compatible with declared fisheries policies of a few countries, e.g. with regard to whaling, sealing, and indiscriminate biomass fishing, it is not only incompatible with the basic tenets of fisheries science, but also with the vision, gradually emerging globally, that marine organisms such as marine mammals, sea turtles, sea-birds and other fauna have an intrinsic value and right to life that should not be undermined by more of the indiscriminate fishing which currently shapes much of our interactions with the oceans.  相似文献   

半干旱区雨水集流研究进展及其现状   总被引：24，自引：5，他引：19  

李小雁  龚家栋 《中国沙漠》2002,22(1):88-92

论述了国内外半干旱区雨水集流研究的发展和存在问题。国外雨水集流研究的发展可分为三个阶段:20世纪50年代以前为雨水的初始利用阶段;20世纪50年代到80年代为基础性研究和技术开发大发展阶段;20世纪80年代以后为系统研究阶段。国内雨水集流研究相对较晚,20世纪60年代为初步研究阶段,20世纪80年代以后为系统研究阶段。集水技术操作简单,适应性强,费用低,开发潜力大,从事的生产领域广泛,采用这种技术可以建立新的农业生态系统并改善半干旱区生态环境。  相似文献