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31.
The land evaluation and site assessment (LESA) method has been used extensively in the United States to assess agricultural
land suitability for different localities. Despite widespread use, LESA models rarely have been evaluated in a systematic,
comprehensive manner. This article discusses development of a LESA system for Hawaii, the first statewide application of the
LESA methodology. The empirical model was implemented with a computerized geographic information system (GIS). The system's
efficiency, ability to discriminate among land parcels, and robustness to subjective model parameter values are evaluated
with statistical analyses and map overlays of GIS data. Results show great potential to simplify the original model specification,
primarily through deletion of marginal site assessment factors. System output was generally insensitive to the numeric values
selected for model parameters, with exception of the ratio used to combine the land evaluation (LE) and site assessment (SA)
component scores. Relative supplies of the differing land attributes measured by the two components must be considered in
determining an appropriate LE:SA ratio for a given area. 相似文献
32.
Heinz G. Stefan .Ruochuan Gu 《Journal of the American Water Resources Association》1991,27(6):967-978
ABSTRACT: Forced artificial mixing of temperature-stratified ponds, or small lakes or reservoirs, by liquid jets can enhance water quality and can also be energy efficient. Based on previous studies of jet mixing mechanics of stratified water bodies, a conceptual design approach is presented. The main “operational” and “system” design parameters are considered in the proposed method. Using minimization of a total cost estimate as a criterion, an iterative method for the selection of the number and size of the jets is developed and illustrated. 相似文献
33.
Large-scale constructed wetlands for nutrient removal from stormwater runoff: An everglades restoration project 总被引:14,自引:0,他引:14
Mariano Guardo Larry Fink Thomas D. Fontaine Susan Newman Michael Chimney Ronald Bearzotti Gary Goforth 《Environmental management》1995,19(6):879-889
The South Florida Water Management District (SFWMD) constructed a wetland south of Lake Okeechobee to begin the process of
removing nutrients (especially phosphorus) from agricultural stormwater runoff entering the Everglades. The project, called
the Everglades Nutrient Removal (ENR) project, is a prototype for larger, similarly constructed wetlands that the SFWMD will
build as part of the Everglades restoration program. This innovative project is believed to be one of the largest agricultural
stormwater cleanup projects in the United States, if not in the world. This publication describes the ENR project's design,
construction, and proposed operation, as well as the proposed research program to be implemented over the next few years. 相似文献
34.
本文分析了江苏省近几十年来、特别是80年代以来冬季气温的变化特征,根据农业灾害发生的条件,讨论了“暖冬”对农业生产及农业灾害的影响,为农业生产部门和防灾抗灾部门决策提供科学依据. 相似文献
35.
Fertilizer Management in Watersheds of Two Ramsar Wetlands and Effects on Quality of Inflowing Water
Two field experiments were carried out in the watersheds of two Ramsar wetland areas, Lakes Koronia and Volvi (area A) and
Lakes Mikri and Megali Prespa (area B), to study the effect of application of N fertilizer on wheat yields, the quality of
runoff water, and the quality of stream water. The treatments were a combination of two methods of fertilizer application
(total amount in fall, and 2/3 in fall + 1/3 in spring) at three rates (0, 100, and 200 kg N/ha) with four replications. Concentrations
of NH4
+, NO3
−, NO2
−, P, and Cl− and pH were determined in all water samples. Runoff water quality was not influenced by fertilizer application in either
area. Chemical parameters for water did not differ along the selected watercourses in area B, while in area A they were higher
in the samples taken near Lake Koronia than in the samples taken upstream, indicating that the watercourses are polluted downstream
by nonagricultural sources. The differences in wheat yields between the 100 and 200 kg N/ha application rates were not high.
These results call for better fertilizer management in order to achieve better yields and to diminish the possibility to have
negative effects to the environment. 相似文献
36.
我国是发展中的国家,农业在国民经济中占有十分重要的地位,环境污染和生态破坏是农业潜伏着的生态危机,也是农业发展过程中亟待解决的重大问题。如何从我国农业环境问题的特点和农业经济现状出发,制定出与农业经济发展相适应遥农业环境保护战略,是我国农业发展和环境保护工作中的一项重要任务。本文就我国农业环境保护的战略地位和作用、指导思想和方针、目标和重点、措施等一系列战略问题,进行初步探讨。 相似文献
37.
Human impacts on the stream-groundwater exchange zone 总被引:13,自引:0,他引:13
Hancock PJ 《Environmental management》2002,29(6):763-781
Active exchanges of water and dissolved material between the stream and groundwater in many porous sand- and gravel-bed rivers
create a dynamic ecotone called the hyporheic zone. Because it lies between two heavily exploited freshwater resources—rivers
and groundwater—the hyporheic zone is vulnerable to impacts coming to it through both of these habitats. This review focuses
on the direct and indirect effects of human activity on ecosystem functions of the hyporheic zone. River regulation, mining,
agriculture, urban, and industrial activities all have the potential to impair interstitial bacterial and invertebrate biota
and disrupt the hydrological connections between the hyporheic zone and stream, groundwater, riparian, and floodplain ecosystems.
Until recently, our scientific ignorance of hyporheic processes has perhaps excused the inclusion of this ecotone in river
management policy. However, this no longer is the case as we become increasingly aware of the central role that the hyporheic
zone plays in the maintenance of water quality and as a habitat and refuge for fauna. To fully understand the impacts of human
activity on the hyporheic zone, river managers need to work with scientists to conduct long-term studies over large stretches
of river. River rehabilitation and protection strategies need to prevent the degradation of linkages between the hyporheic
zone and surrounding habitats while ensuring that it remains isolated from toxicants. Strategies that prevent anthropogenic
restriction of exchanges may include the periodic release of environmental flows to flush silt and reoxygenate sediments,
maintenance of riparian buffers, effective land use practices, and suitable groundwater and surface water extraction policies. 相似文献
38.
Three mathematical models, the runoff curve number equation, the universal soil loss equation, and the mass response functions,
were evaluated for predicting nonpoint source nutrient loading from agricultural watersheds of the Mediterranean region. These
methodologies were applied to a catchment, the gulf of Gera Basin, that is a typical terrestrial ecosystem of the islands
of the Aegean archipelago. The calibration of the model parameters was based on data from experimental plots from which edge-of-field
losses of sediment, water runoff, and nutrients were measured. Special emphasis was given to the transport of dissolved and
solid-phase nutrients from their sources in the farmers' fields to the outlet of the watershed in order to estimate respective
attenuation rates. It was found that nonpoint nutrient loading due to surface losses was high during winter, the contribution
being between 50% and 80% of the total annual nutrient losses from the terrestrial ecosystem. The good fit between simulated
and experimental data supports the view that these modeling procedures should be considered as reliable and effective methodological
tools in Mediterranean areas for evaluating potential control measures, such as management practices for soil and water conservation
and changes in land uses, aimed at diminishing soil loss and nutrient delivery to surface waters. Furthermore, the modifications
of the general mathematical formulations and the experimental values of the model parameters provided by the study can be
used in further application of these methodologies in watersheds with similar characteristics. 相似文献
39.
Integrated Resource Management: Moving from Rhetoric to Practice in Australian Agriculture 总被引:1,自引:0,他引:1
/ Implementing the concept of sustainability through integrated approaches to natural resource management poses enormous challenges for both the rural communities and government agencies concerned. This paper reviews the underlying rhetoric of sustainable agricultural systems and the integrated resource management paradigm and identifies some of the challenges being experienced in translating this rhetoric into practice. A relatively recently implemented community-based integrated catchment management (ICM) process in a rural community in northeast Australia is examined in terms of some of the lessons learned that may be relevant to other similar integrated resource management (IRM) processes. It reveals a pragmatic, opportunistic, and evolving implementation process based on adaptive learning rather than a more traditional "rational" planning approach. Some essential characteristics of a community-based IRM process are identified, including fostering communication; providing a structure that fosters cooperation and facilities coordination among community, industry, and government agencies; the integration of IRM principles into local government planning schemes; and an emergent strategic approach to IRM program implementation. We conclude by identifying some essential characteristics of an IRM process that can assist a community to adapt to, and manage change for, sustainable resource use. 相似文献
40.
Saber A. El-Shafai Fatma A. El-Gohary Fayza A. Naser P. van der Steen Huub J. Gijzen 《The Environmentalist》2007,27(2):287-302
An integrated system, consisting of Up-flow Anaerobic Sludge Blanket (UASB)-duckweed-tilapia ponds was used for recovery of
sewage nutrients and water recycling. A UASB reactor with 40 liter working volume was used as pre-treatment unit followed
by a series of three duckweed ponds for nitrogen recovery. The treated effluent and duckweed biomass was used to feed fishponds
stocked with Nile tilapia (Oreochromis niloticus). The UASB reactor was fed with raw, domestic sewage at 6 h hydraulic retention time. The three duckweed ponds were stocked
with Lemna gibba and fed with UASB effluent at 15 days hydraulic retention time. Nitrogen recovery from UASB effluent via duckweed biomass
represented 81% of total nitrogen removal and 46.5% from the total nitrogen input to the system. In subsequent fishponds the
nitrogen recovery from duckweed as fish feed was in the range of 13.4–20%. This nitrogen in fish biomass represented 10.6–11.5
g N from the total nitrogen in the raw sewage fed to the UASB reactor. The growth performance of tilapia (Oreochromis niloticus) showed specific growth rates (SGR) in the range of 0.53–0.97. The range of feed conversion ratio (FCR) and protein efficiency
ratio (PER) were 1.2–2.2 and 2.1–2.28, respectively. The results of the experiments showed total fish yield and net fish yield
in the range of 17–22.8 ton/ha/y and 11.8–15.7 ton/ha/y respectively. In conclusion UASB-duckweed-tilapia ponds provide marketable
by-products in the form of duckweed and fish protein, which represent a cost recovery for sewage treatment. 相似文献