首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
The main goal of this study is the derivation of Carlson’s Trophic State Index (TSI) through the remote sensing of four different Case-2 waters in the Mediterranean region such as Cyprus and Greece. TSI SD is derived through extensive field ground campaign of Secchi Disk Depth measurements for the Asprokremmos Dam, located in Paphos District in Cyprus; Alyki Salt Lake, located in Larnaca District in Cyprus; and in Karla Lake, located in Volos District in Greece; and finally to three coastal water areas in the Limassol coastal area. Several regression models have been applied in order to develop the best regression model between the TSI SD and in-band reflectance values for Landsat TM/ETM derived from spectroradiometric measurements using a GER-1500 field spectroradiometer over the main case study area in Asprokremmos Dam in Cyprus. Finally, we apply several regression models for Asprokremmos Dam for retrieving the suitable Landsat TM/ETM band or band combinations (obtained from field spectroradiometric measurements) in which TSI SD can be determined. Indeed, the best regression model has been obtained by correlating ‘TSI Versus Band2/Band3’, with R2=0.89. All field TSI SD and in-band reflectance values from the four different water bodies have been used to develop the best fitted model for the established TSI SD Versus Band2/Band3 model. We find that the exponential regression model provides the best fitted equation over the four different water bodies.  相似文献   

2.
Particulate matter concentration and assessment of its movement pattern is crucial in air pollution studies. However, no study has been conducted to determine the PM10 concentration using atmospheric correction of thermal band by temperature of nearest dark pixels group (TNDPG) of this band. For that purpose, 16 Landsat Enhanced Thematic Mapper plus ETM+ images for Sanandaj and Tehran in Iran were utilized to determine the amount of PM10 concentration in the air. Thermal infrared (band 6) of all images was also used to determine the ground station temperature (GST b6) and temperature of nearest dark pixels group. Based on atmospheric correction of images using temperature retrieval from Landsat ETM+, three empirical models were established. Non-linear correlation coefficient with polynomial equation was used to analyze the correlations between particulate matter concentration and the ground station temperature for the three models. Similar analyses were also undertaken for three stations in Klang Valley, Malaysia, using 11 Landsat ETM+ images to show the effectiveness of the model in different region. The data analysis indicated a good correlation coefficient R = 0.89 and R = 0.91 between the trend of the result of temperature of nearest dark pixels group b6 ? (GST b6 ? GST) model and the trend of PM10 concentration in Iran and Malaysia, respectively. This study reveals the applicability of the thermal band of Landsat TM and ETM+ to determine the PM10 concentration over large areas.  相似文献   

3.
This paper aims to reveal the reciprocal influence of Kürtün Dam and wastewaters from the settlements on the water quality in the stream Har?it, NE Turkey. Several key water-quality indicators were measured: water temperature (T), pH, dissolved oxygen (DO), electrical conductivity, water hardness, chemical oxygen demand (COD), ammonium nitrogen (NH4 +–N), nitrite nitrogen (NO2 ?–N), nitrate nitrogen (NO3 ?–N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), orthophosphate phosphorus (PO4 3?–P), and methylene blue active substances (MBAS). The monitoring and sampling studies were conducted every 15 days from March 2009 to February 2010 at two stations selected in the upstream and downstream of the Kürtün Dam. It was concluded that the Kürtün Dam Lake had a high-quality water in terms of T, pH, DO, COD, NH4 +–N, NO2 ?–N and NO3 ?–N values, but slightly polluted water with respect to TKN, PO4 3?–P, and MBAS according to the Turkish Water Pollution Control Regulation. The dam improved the stream water quality by increasing the DO concentration, and decreasing the NO2 ?–N and PO4 3?–P concentrations thanks to its hydraulic residence time despite the wastewater discharge by the nearby settlements. However, the wastewater discharge deteriorated the stream water quality increasing the COD, NH4 +–N, NO3 ––N, and TN concentrations.  相似文献   

4.
卫星传感器波段平均太阳辐照度(solar exoatmospheric spectral irradiances,简称ESUN)是反演地表温度、大气顶部反射率的重要参数。目前,Landsat 8卫星的传感器ESUN值美国地质调查局仍未公布。采用ChKur、WRC、Thuillier、ASTM和Wehrli太阳光谱数据,结合Landsat 8卫星的相对光谱响应数据,使用代入计算的方法分别计算了OLI传感器各波段的ESUN值。与ChKur数据计算的结果相比,应用Wehrli数据计算的结果均方根误差最小,使用WRC数据计算的结果均方根误差最大。为验证结果,用同样的方法计算了基于ChKur太阳光谱数据的Landsat 7卫星ETM+传感器的ESUN值,并与美国地质调查局官方推荐的结果做对比,结果表明,基于ChKur太阳光谱数据采用该方法计算结果较为符合官方数据。  相似文献   

5.
Forest stand biomass serves as an effective indicator for monitoring REDD (reducing emissions from deforestation and forest degradation). Optical remote sensing data have been widely used to derive forest biophysical parameters inspite of their poor sensitivity towards the forest properties. Microwave remote sensing provides a better alternative owing to its inherent ability to penetrate the forest vegetation. This study aims at developing optimal regression models for retrieving forest above-ground bole biomass (AGBB) utilising optical data from Landsat TM and microwave data from L-band of ALOS PALSAR data over Indian subcontinental tropical deciduous mixed forests located in Munger (Bihar, India). Spatial biomass models were developed. The results using Landsat TM showed poor correlation (R2 = 0.295 and RMSE = 35 t/ha) when compared to HH polarized L-band SAR (R2 = 0.868 and RMSE = 16.06 t/ha). However, the prediction model performed even better when both the optical and SAR were used simultaneously (R2 = 0.892 and RMSE = 14.08 t/ha). The addition of TM metrics has positively contributed in improving PALSAR estimates of forest biomass. Hence, the study recommends the combined use of both optical and SAR sensors for better assessment of stand biomass with significant contribution towards operational forestry.  相似文献   

6.
To assess possible impacts on Lake Pontchartrain fishes from the 2005 hurricanes, we compared trawl, beach seine, and gillnet collections taken before (2000–2003, 2005) and after (2006–2009) to determine if significant assemblage changes occurred. We also compared basic environmental variables to test for hurricane-related changes. Significant post-hurricane changes in fish assemblages occurred in trawl (analysis of similarity (ANOSIM), R?<?0.090, p?<?0.05) and beach seine (ANOSIM, R?<?0.120, p?<?0.05) collections across all seasons. Gillnet assemblages exhibited changes in only one season (ANOSIM, R?=?0.045, p?<?0.05). These consistently low global R values (all R?<?0.120) across all gears suggest only minor compositional changes in species. When peak abundance periods were compared for individual species, Gulf menhaden (Brevoortia patronus) declined in trawl collections after the hurricanes (Friedman's test, χ 2?=?6.00, p?=?0.014) but increased in gillnet collections (Friedman's test, χ 2?=?5.00, p?=?0.025). Hardhead catfish (Ariopsis felis) increased in trawl collections, but Gulf pipefish (Syngnathus scovelli), naked gobies (Gobiosoma bosc), and rough silverside (Membras martinica) all declined in beach seine samples and Atlantic croakers (Micropogonias undulatus), Spanish mackerel (Scomberomorus maculatus), and sand seatrout (Cynoscion arenarius) all declined in gillnet samples. In general, salinity increased and water clarity and dissolved oxygen decreased after the hurricanes. While the overall composition of Lake Pontchartrain fish assemblages remains stable, the significant decline of some species and changes in certain environmental variables are cause for concern. Future monitoring should determine if all elements of this estuary will recover from these impacts.  相似文献   

7.
A single crystal of scolecite, CaAl2Si3O10· 3H2O, was studied by X-ray diffraction methods at room temperature. The intensities were measured with MoKα radiation (λ=0.71069?Å) in a complete sphere of reflection up to sinθ/λ=0.9?Å?1. The structure was refined in the pseudo-orthorhombic setting of space group F1d1 instead of the conventional setting Cc for better comparison with natrolite (Fdd2). The cell parameters are: a=18.502(1)?Å, b=18.974(2)?Å, c=6.525(1)?Å, β=90.615(7)°, V=2290.6(3)?Å3, Z=8. A refinement of high-order diffraction data yielded residuals of R(F)=0.9%, R w (F)=0.9%, GoF=1.73 for 1831 high-angle reflections (0.7≤sinθ/λ≤0.9?Å?1) and R(F)=1.2%, R w (F)=1.4%, GoF=3.22 for all 3478 independent reflections. In comparison with natrolite, the replacement of 2 Na+ by 1 Ca2+ and 1 H2O leads to a reduction of symmetry from Fdd2 to F1d1. Each general atomic position in natrolite (except of Na) splits into two crystallographically independent positions in scolecite. The T?O distances and T?O?T angles of these two sites differ distinctly from each other due to the influence of the calcium ions on the framework. An unexpected result of our detailed analysis of the data is that the additional water molecule (O7) disturbs the symmetry of the framework to a greater extent than the replacement of Na+ by Ca2+. As a comparison of the displacement parameters indicates, the bonds within the tetrahedral framework and to the extraframework cations are stronger in scolecite than in natrolite. The isotropic U(equ) values of the framework atoms and extraframework cations are about 10% smaller in scolecite compared to natrolite. The same tendency is shown by the analysis of the internal vibrational amplitudes ΔU. The corresponding force constants are in the range of F=358 to 3367?Nm?1 for the T?O bonds in scolecite (in natrolite: F=354 to 824?Nm?1). The values of the force constants which determine the vibrations of the Ca ions and water molecules against the framework oxygen atoms lie in the range of F=33 to 1757?Nm?1 (in natrolite: F=57 to 293?Nm?1).  相似文献   

8.
Urbanization has accelerated rapidly over the last century, which has caused surfaces in natural ecosystems to shift to impervious surfaces. As a result, urban watershed ecosystems show altered physical, chemical and ecological process. As an important part of watershed management, urbanization has become one of the key issues involved in the deterioration of water quality. Impervious surface area (ISA) has been recognized as a key indicator of the effects of non-point runoff and water quality within a particular watershed. Numerous case studies have been conducted to investigate the relationship between urbanization and water quality in different study areas. However, there is still a lack of understanding regarding quantitative analysis of the threshold between urbanization and water quality indicators. This study was conducted to improve the understanding of how to quantify a threshold between urbanization and water quality, taking the rapid urbanization zone of Shenzhen, China as a case study. To accomplish this, ISA was extracted from the Landsat? image using a linear spectral mixture method to quantify the urbanization. The relationship between water quality indicators and ISA was then analyzed by nonlinear regression, and the threshold between ISA and the chemical indicators of water quality was investigated using the statistical segment approach method. The results indicate that the water quality indicators and ISA are significantly correlated, and that, with the exception of Zn, Pb, and CN, the water quality indicators had R 2 values greater than 0.45. Furthermore, with the exception of Zn, F?, Pb and oils, water quality indicators were found to have an ISA threshold of 36.9–52.9 %, indicating that it is important to control the ISA below 36.9 % in urbanization watersheds to enable effective urban watershed management.  相似文献   

9.
Concentrations of suspended solids in lakes can affect the latter’s primary productivity and reflect changes in sediment deposition. Determining the temporal and spatial distribution of suspended solid concentrations has important significance in lake water environmental management; this is particularly urgent for Poyang Lake, the largest freshwater lake in China. In this study, suspended solid concentration inversion models for Poyang Lake were created using a semi-empirical method with regression analysis between continuously measured suspended solid concentration data and multi-band moderate-resolution imaging spectroradiometer images for spring, summer, autumn, and winter from 2009 to 2012. The coefficient of determination (R2) is from 0.6 to 0.9 and the average relative error for the accuracy verification was between 10 and 30%. The seasonal distributions of suspended solid concentrations in Poyang Lake from 2000 to 2013 were then obtained using optimal reversal models. The results showed that the seasonal variation in suspended solid concentrations had a “W” shape in which high spring and autumn and low summer and winter values. The suspended solid concentrations increased annually from 2000 to 2013 and were mainly distributed in the northern and central portions of the lake, with lower values along the shorelines. Further analysis indicated that the large difference in water level between the wet and dry seasons is an important factor in explaining these seasonal variations. Moreover, the suspended solid concentrations were poorly correlated with water temperature and chlorophyll-a concentration but more highly correlated with the deferred chlorophyll-a concentration.  相似文献   

10.
一种页岩含气性热演化规律研究的模拟实验方法   总被引：2，自引：1，他引：1  
目前针对页岩气赋存规律研究的热模拟实验主要是沿袭常规油气热模拟方法,以粉末态样品开展模拟,研究对象为岩石生成并排出的烃类气体,这种模拟方式未明确页岩气的实质为"滞留气",并且模拟后样品无法开展扫描电镜分析,不能确定岩石孔隙结构变化规律。本文通过石英玻璃管封装块状样开展页岩生烃热模拟实验,并结合一套数据处理方法,尝试建立了一种适合页岩气研究的热模拟实验方法,研究泥页岩在不同演化阶段(Ro范围为0.596%~2.143%)不同赋存状态气体的含量以及岩石微观孔隙特征的变化情况。结果表明,泥岩及油页岩样品的排出气及解析气含量在高成熟度阶段(400℃以后)有明显增加的趋势,结合扫描电镜微观结构分析显示这是由于有机质生气量以及无机孔隙均有增加。本方法可以研究页岩热演化过程中不同赋存状态气体含量及微观孔隙结构的变化,为页岩气勘探开发提供了一种可参考的方法。  相似文献   

11.
To quantitatively analyze the response of distributions and hydrogen isotopic compositions （SD） of plant leaf wax to moisture, and to better understand their implications for paleoclimatic reconstruction, we measured av- erage chain length （ACL） and 8D values of n-alkanes and n-fatty acids （n-FAs） from Orinus kokonorica, a typical and representative plant in Lake Qinghai area, along a distance transect extending from lakeshore to wetland to dry- land in the arid ecosystem. The results showed that the ACL values of n-alkanes and n-FAs were negatively corre- lated with soil water content （SWC） with R2~0.593 and R2=0.924, respectively. This is as a result of plant＇s response to water loss with more abundance in long-chain n-alkyl lipids under increasing aridity by analyzing relationships between the molecular ratios of long-chain n-alkyl lipids （n-alkanes and n-FAs） from O. kokonorica and SWC. The 8D values of C29 n-alkane and C28 n-FA were also negatively correlated with SWC with R2-0.778 and R2-0.760, respectively, which may due to enhanced D-enrichment in leaf water by evapotranspiration （soil water evaporation and leaf water transpiration） with increasing aridity. Our results demonstrated that moisture exerts a significant con- trol on the ACL and 8D values from O. kokonorica in an arid ecosystem. This preliminary study on a modern single plant （O. kokonorica） sets a foundation for comprehending these values as quantitative proxies for paleo-humidity reconstruction.  相似文献   

12.
One of the most important qualitative aspects of wetland ecosystem management is preserving the natural quality of water in such environments. This would not be achievable unless continuous water quality monitoring is implemented. With the recent advances in remote sensing technology, this technology could assist us to produce accurate models for estimating water quality variables in the ecosystem of wetlands. The present study was carried out to evaluate the capability of remote sensing data to estimate the water quality variables [pH, total suspended solids (TSS), total dissolved solids (TDS), turbidity, nitrate, sulfate, phosphate, chloride and the concentration of chlorophyll a] in Zarivar International Wetland using linear regression (LR) and artificial neural network (ANN) models. For this purpose, spectral reflectance of bands 2, 3, 4 and 5 of the OLI sensor of Landsat 8 was utilized as the input data and the collected chemical and physical data of water samples were selected as the objective data for both ANN and LR models. Based on our results overall, ANN model was the proper model compared with LR model. The spectral reflectance in bands 5 and 4 of OLI sensor revealed the best results to estimate TDS, TSS, turbidity and chlorophyll in comparison with other used bands in ANN model, respectively. We conclude that OLI sensor data are an excellent means for studying physical properties of water quality and comparing its chemical properties.  相似文献   

13.
A comprehensive assessment on lake water quality was carried out in Shahu Lake, northwest China, to provide valuable information about present lake water quality for decision making. Major ions, general parameters, bacteriological parameters, organics and trace metals monitored monthly in 2014 were considered. Monitored parameters were compared with quality criteria for surface water of China, and overall water quality assessment was carried out using an entropy weighted water quality index (EWQI) based on 20 selected parameters. Lake water quality was also assessed for irrigation purpose. The results show that the lake water is of Cl·SO4–Na facies with high salinity and COD. The geochemistry of the lake water is regulated by intense evaporation and human activities. TP, TN and F? are major inorganic contaminants, with over 50% of the water samples polluted by them. Oil, mainly attributed by leaky motor tourist boats, is the major organic pollutants in the lake water, with 10 samples (37.04%) showing higher oil content than the permissible limit. The concentrations of other inorganic and organic contaminants as well as trace metals are well below the permissible limits. The present study indicates that inorganic contamination in the lake water is more severe than organic pollution. The overall lake water quality, assessed by EWQI, is poor and very poor with SO4 2?, TDS, TH and Cl? being the dominant contributing factors. The lake water is suitable for irrigation in terms of alkalinity, but is unsuitable for irrigation from the salinity point of view. Accelerating the circulation and replenishment of the lake water is an important way of reducing contaminant concentrations. This study is important in providing comprehensive information on lake water quality for decision makers and valuable reference for international lake water researchers.  相似文献   

14.
The objective of the current study is to use satellite data to assess the mutual influence between vegetation and climate. The Ismailia Governorate was selected as a case study to investigate the impact of vegetation cover expansion on both land surface and air temperature from 1983 to 2010 and vice versa. This observation site was carefully selected as a clear example of the high rate of the reclamation and vegetation expansion process in Egypt. Land surface temperature (LST) was estimated through the Advanced Very High Resolution Radiometer (a space-borne sensor embarked on the National Oceanic and Atmospheric Administration) data while air temperature (T air) was collected from ground meteorological stations in the study area. Irrigated agriculture is the largest consumer of freshwater resources. However, consistent information on irrigation water use is still lacking. Relative humidity, wind speed, solar radiation, and T air data were inserted in the Penman–Monteith equation to calculate potential evapotranspiration (ETo), while both LST and T air were used to observe the relative water status of the study area as a result of the water deficit index (WDI). Then, both WDI and ETo were used to calculate actual evepotranspiration (ETC.). The results showed that LST decreased by about 2.3 °C while T air decreased by about 1.6 °C during the study period. The results showed also that the vegetation cover expanded from 25,529.85 ha in 1985 to 63,140.49 ha in 2009 with about 147 % increase. This decrease in LST and air temperature was according to the expansion of the cultivated land that was proved through the processing of three Landsat TM and Landsat ETM+ imageries acquired in June 19, 1985, June 7, 1998, and June 29, 2009. The vegetation water consumption was affected by the decreasing surface and air temperature. The results showed that the water deficit index decreased by about 0.35, and actual evapotranspiration increased by about 2.5 mm during the study period.  相似文献   

15.
The occurrence of increasing blooms of toxic cyanobacteria in freshwaters has received much attention due to the ability of many cyanobacteria to produce potent cyanotoxins. In this paper, the occurrence of dominant cyanobacteria and the concentration of microcystins (MCs) analysis were investigated monthly from July 2008 to April 2009 in the Hoan Kiem Lake and from February to April 2009 in the Nui Coc reservoir. Concentrations of intracellular MCs from water, bloom samples, and isolated strains were quantified by using high performance liquid chromatography (HPLC). During the study period, the microscopic examination of the phytoplankton samples showed the dominance of the genus Microcystis in the water environment of the Hoan Kiem Lake and the Nui Coc reservoir. The toxin analysis by HPLC demonstrated the presence of two MC variants: MC-LR and MC-RR in water samples. Total concentrations of the toxins in filtered samples from surface water ranged from non-detected to 0.91 μg L?1 at Nui Coc reservoir and they ranged from 2.1 to 46.0 μg L?1 at Hoan Kiem Lake. The results of the HPLC analysis confirmed the production of MCs in bloom samples (ranged from 115.9 to 184.6 μg L?1 in the Hoan Kiem Lake and from 726.5 to 1116 μg L?1 in the Nui Coc reservoir) and isolated strains of Anabaena sp. and Microcystis with the concentration of MC ranging from 152 to 396.2 μg g?1 dry mass, respectively.  相似文献   

16.
It is important to have qualitative as well as quantitative understanding of the hydraulic exchange between lake and groundwater for effective water resource management. Dal, a famous urban fresh water lake, plays a fundamental role in social, cultural and economic dynamics of the Kashmir Valley. In this paper geochemical, isotopic and hydrological mass balance approaches are used to constrain the lake water–groundwater interaction of Dal Lake and to identify the sources of lake water. Water samples of precipitation (n = 27), lake water (n = 18) and groundwater (n = 32) were collected across the lake and its catchment for the analysis of δ18O and δ2H. A total of 444 lake water samples and 440 groundwater samples (springs, tube wells and dug wells) were collected for the analysis of Ca2+, Mg2+, HCO3 ?, SO4 2?, Cl?, NO3 ?, Na+ and K+. Water table and lake water level were monitored at 40 observation locations in the catchment. Water table map including pH and EC values corroborate and verify the gaining nature of the Dal Lake. Stable isotopes of lake water in Boddal and Gagribal basins showed more deviation from the global meteoric water line than Hazratbal and Nigeen basins, indicating the evaporation of lake water. The isotopic and geochemical mass balance suggested that groundwater contributes a significant proportion (23–40%) to Dal Lake. The estimated average groundwater contribution to Dal Lake ranged from 31.2 × 103 to 674 × 103 m3 day?1 with an average of 276 × 103 m3 day?1. The study will be useful to delineate the possible sources of nutrients and pollutants entering the lake and for the management of lake water resources for sustainable development.  相似文献   

17.
The decline of submersed aquatic vegetation (SAV) in tributaries of the Chesapeake Bay has been associated with increasing anthropogenic inputs, and restoration of the bay remains a major goal of the present multi-state “Bay Cleanup” effort. In order to determine SAV response to water quality, we quantified the water column parameters associated with success of transplants and natural regrowth over a three-year period along an estuarine gradient in the Choptank River, a major tributary on the eastern shore of Chesapeake Bay. The improvement in water quality due to low precipitation and low nonpoint source loadings during 1985–1988 provided a natural experiment in which SAV was able to persist upstream where it had not been for almost a decade. Mean water quality parameters were examined during the growing season (May–October) at 14 sites spanning the estuarine gradient and arrayed to show correspondence with the occurrence of SAV. Regrowth of SAV in the Choptank is associated with mean dissolved inorganic nitrogen <10 μM; mean dissolved phosphate <0.35 μM; mean suspended sediment <20 mg l?1; mean chlorophylla in the water column <15 μg l?1; and mean light attenuation coefficient (Kd) <2 m?1. These values correspond well with those derived in other parts of the Chesapeake, particularly in the lower bay, and may provide managers with values that can be used as target concentrations for nutrient reduction strategies where SAV is an issue.  相似文献   

18.
An ephemeral estuarine turbidity maximum (ETM) occurs at high water in the macrotidal Taf estuary (SW Wales, United Kingdom). A new mechanism of ETM formation, due to resuspension and advection of material by flood tidal currents, is observed that differs from classical mechanisms of gravitational circulation and tidal pumping. The flood tide advances across intertidal sand flats in the main body of the estuary, progressively entraining material from the rippled sands. Resuspension creates, a turbid front that has suspended sediment concentrations (SSC) of about 4,000 mg I−1 by the time it reaches its landward limit which is also the landward limit of salt penetration. This turbid body constitutes the ETM. Deposition occurs at high slack water but the ETM retains SSC values up to 800 mg I−1, 1–2 orders of magnitude greater than ambient SSC values in the river and estuarine waters on either side. The ETM retreats down the estuary during the ebb; some material is deposited thinly across emergent intertidal flats and some is flushed out of the estuary. A new ETM is generated by the next flood tide. Both location and SSC of the ETM scale on Q/R3 where Q is tidal range and R is river discharge. The greatest expression of the ETM occurs when a spring tide coincides with low river discharge. It does not form during high river discharge conditions and is poorly developed on neap tides. Particles in the ETM have effective densities (120–160 kg m−3) that are 3–4 times less than those in the main part of the estuary at high water. High chlorophyll concentrations in the ETM suggest that flocs probably originate from biological production in the estuary, including production on the intertidal sand flats.  相似文献   

19.
Sediment discharge due to soil and rock erosion within the watersheds is the major cause of siltation in water reservoirs. Siltation in reservoirs reduces the capacity for power production, irrigation water supply, and other domestic purposes. Hypsometric analysis has widely been used to identifying the geomorphic development stages (stabilized, equilibrium, and un-stable) to assess the erosion proneness of watersheds. In this study, watershed of Kurram Tangi Dam and its four sub-watersheds (SWs) were considered to determine their sediment discharge capacity through hypsometric analysis. The boundaries of watershed and sub-watersheds were delineated from Digital Elevation Model (DEM). The hypsometric parameters i.e., hypsometric integral (HI) and curves were generated using Geographic Information System (GIS) techniques. The HI values of SW-1 (0.41) and SW-2 (0.36) indicated that these two SWs were relatively more prone to erosion and contributed higher sediment discharge in Dam siltation. The results were validated through sampling the main drainage channel (Kurram River) to determine the sediment concentration at 12 sites during summer, winter, and spring seasons. Comparison of HI and sediment concentration of SWs presented high correlation (R2?=?0.87). The results emphasized the effective watershed management, extensive afforestation, and construction of silt-control structures at appropriate locations in sub-watersheds. This will ultimately maintain the water and power generation capacity as well as extending the life span of the Dam.  相似文献   

20.
Suspended sediment concentration (SSC) is an important parameter for monitoring coastal water quality. Suspended particles are also the main optically active substances for ocean color remote sensing. It is important to study the surface reflectance spectra features of coastal turbid water, as it can be the basis for establishing more accurate remote-sensing inversion models. In this study, Hangzhou Bay, China, was selected as the study area. Two in situ measurement and sampling stations in the estuary of the Qiantang River which flows into Hangzhou Bay were set up separately. Above-water spectrum observation method, which the NASA recommended, was adopted to measure the reflection spectrum of turbid waters. Surface water samples were simultaneously collected to obtain the corresponding SSC data. The results showed that the total suspended particle concentrations in the Hangzhou Bay were typically high, and the inorganic suspended particle concentrations were far greater than the phytoplankton concentrations, which averages 705?mg/L and 1.16?mg/m3. The SSC at two sampling stations both showed significant temporal variability, particularly appearing short-period rapid fluctuations accompanying the tidal cycle. The measured surface water reflectance spectra all showed typical curve characteristics of high turbid water, and as the SSC increased, the corresponding reflectivity of surface water also increased. The increments at different wavelengths were variational, with two reflectance peaks appearing at 650?C700-nm and near the 800-nm wavelength of spectral curves, respectively. The first derivative of spectral curves showed that the first reflectance peak location appeared to be a ??red shift?? phenomenon with the SSC increasing. The correlation coefficients between the SSC of surface water and the remote-sensing reflectance according to moderate resolution imaging spectra-radiometer (MODIS) channels?? central wavelength were different significantly, which were larger at MODIS long-wavelength channels (>650?nm) and smaller at MODIS short-wavelength channels (400?C550?nm). The value of determination coefficient R 2 was 0.82 when the reflectance ratio of MODIS band 2 to band 1 was selected as the SSC sensitive bands combination and exponential regression analysis was employed. Therefore, the reflectance ratio of MODIS band 2 to band 1 can be adopted as the main band combination for establishing surface water SSC remote-sensing inversion model in the Hangzhou Bay.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号