A modified TOPMODEL introducing the bedrock surface topographic index in Huangbengliu watershed,China

Subsurface stormflow is a dominant runoff mechanism in steep humid mountainous areas.An insite measurement of subsurface stormflow suggests that the bedrock surface plays an important role in the runoff generation and routing process,which was rarely adopted in hydrological modelling studies.To improve the runoff simulation performance,the bedrock surface topographic index is introduced,and a modified TOPMODEL based on the bedrock surface topographic index is developed to simulate the runoff.The modified TOPMODEL is applied to the Huangbengliu(HBL),a steep watershed in Gongga Mountain,and proved to be more appropriate for the HBL watershed,especially for peak simulation.The Nash-Sutcliffe model efficiency(NSE)is improved from 0.24 to 0.58 in the calibration period and from 0.40 to 0.62 in the verification period.The result of this study can advance the understanding of the mechanism of flash floods and contribute flood control and disaster prevention in the HBL watershed and similar areas.

An Efficient Method on Deriving Topographic Index from DEM for Land Surface Hydrological Model Simulations

As a kernel parameter of the TOPMODEL-concept-based land surface model （LSM）, topographic in- dex （TI） is commonly derived from high resolution digital elevation model （DEM）. Various approaches to compute TI by using different algorithms have been developed in previous literature. However, fiat areas and pits in DEMs of real watershed sometimes impose an arbitrary and spatially constant drainage density which may cause conventional retrieval methods to be very computer-intensive, especially for regional or global climate simulations where rugged mountainous areas are mixed with fiat terrains in the DEM. In this paper, we propose a new approach to overcome this shortcoming by introducing a quantile classification to sort the DEM into eight categories at first and then using a fast and simple algorithm to process the fiat areas, fill up pits in the DEM, and make it undulating. Thereafter, the algorithm can be directly applied to assigning flow directions of each cell of the processed DEM rather than taking the complicated approach of Jenson and Domingue. This approach dramatically promotes the computing efficiency with a much easier and faster processing. In addition, the effects of different TI computing approaches on the TOPMODEL-concept-based hydrological simulations are investigated based on experimental simulations over a small-scale watershed gauged by the Yonshuijie hydrological station and a large-scale watershed controlled by the Hanzhong hydrological station, respectively. The results show that the new approach is 13 times faster than the conventional one in TI retrieving, and no evident differences are found in rainfall- runoff simulations when using different algorithms in TI computations. These suggest that the proposed new approach for TI computation can be taken as an alternative and used in the TOPMODEL-concept- based hydrological simulations owning to its simplicity and high efficiency, especially for relevant regional and global studies.

Understanding the spatial distribution of hydrologic sensitive areas in the landscape using soil topographic index approach

Maintaining healthy watershed is pivotal to ensure sustainability in water resources thereby improving the carrying capacity of the earth.Understanding and identifying the spatial variability of hydrologically sensitive areas(HSAs)in a watershed is an important step to prioritizing the landscape to maintain water sustainability with limited resources.A spatial technique known as Soil Topographic Index(STI)was used to identify HSAs in the landscape.This study was conducted in Clinton and Tewksbury Townships in New Jersey,United States.Three different scenarios(STI>=9,STI>=10,and STI>=11)were conducted to understand the spatial distribution of HSAs in the watershed.The following conclusions were derived from this study.Firstly,a more detail representation of HSAs in the watershed was observed when applying the STI technique with a fine scale light detection and ranging(LiDAR)digitial elevation model.Secondly,all three scenarios consistently identified perennial stream corridors as HSAs;therefore,it is important to protect perennial stream corridors through implementation of various land use controls.Thirdly,this study analyzes the land use pattern of HSAs under the three scenarios and identifies the HSAs for high intensity land uses such as agriculture and urban to be the high priority locations for implementing best management practices for water quality improvements.The procedures developed in this study can be applied to watersheds in other parts of the world with similar physiographic characteristics.

Correlation between visual function and refractive,topographic, pachymetric and aberrometric data in eyes with keratoconus

AIMTo analyze the relationship between two visual functions and refractive, topographic, pachymetric and aberrometric indicators in eyes with keratoconus.METHODSCorrected distance visual acuity (CDVA), and letter contrast sensitivity (CS) were correlated with refraction, corneal topography, pachymetry, and total corneal wavefront data prospectively in 71 eyes with keratoconus. The topographic indices assessed were simulated keratometry for the flattest and steepest meridians (SimK1 and SimK2), posterior steeper K (Ks), elevation value in best-fit sphere (BFS) maps, squared eccentricity (Є2), aspheric asymmetric index (AAI), pachymetry, thickness progression index (TPI), the amount of pachymetric decentralization (APD), and GalileiTM-keratoconus indices.RESULTSThe mean CDVA (expressed as logMAR) were 0.25±0.21. The mean CS was 1.25±0.46. The spherical refraction correlated well with CDVA (r=-0.526, P<0.001). From topographic indices, SRI correlated with CS (r=-0.695), and IAI with CS (r=-0.672) (P<0.001 for all). Root mean square (RMS) was 4.3±1.81 µm, spherical aberration (SA) was -0.4±0.67 µm, vertical and horizontal coma were -2.1±1.47 and -0.4±0.72 µm. All wavefront data (except horizontal coma), AAI, Є2 and maximum BFS correlated significantly with the visual function (P≤0.001 for all).CONCLUSIONIn this study, CS is more affected than CDVA as a visual function. The quantity and quality of vision is significantly correlated with well-known and new topographic indices. There is not a significant correlation between visual function and pachymetric parameters. The significantly correlated indices can be used in staging keratoconus and to follow the outcome of a treatment.

Relationship between ponding and topographic factors along the China-Russia Crude Oil Pipeline in permafrost regions

The original landform along the China Russia Crude Oil Pipeline(CRCOP,line 2)was disturbed during installation of pavement for the pipeline.Forest and vegetation coverage is dense,and runoff develops along the pipe.Since the opera tion of the CRCOP(line 2)began in 2018,ponding has appeared on both sides of the pipeline.If there is no drainage,ponding can hardly dissipate,due to the low permeability of the permafrost layer.With the supply of surface flow and the transportation of oil at positive temperatures,ponding promotes an increase in temperature and changes the boundary ther mal conditions of the pipeline.Meanwhile,when the ponding freezes and thaws,frost heave threatens operational safety of the pipeline.Furthermore,the ponding can affect the thermal condition of line 1.In this paper,the distribution of pond ing along the CRCOP was obtained by field investigation.The type and cause of ponding were summarized,and the catch ment and stream order were extracted by the Digital Elevation Model(DEM).According to the statistical results in attri butes for topographic factors,it is known that ponding along the pipeline is relative to elevation,slope,aspect,and the Topographic Wetness Index(TWI).Water easily accumulates at altitudes of 300450 m,slopes within 3°5°,aspect in the northeast or south,TWI within 1316,flow direction in north east south,and flow length within 90150 km.This paper proposes a theoretical basis for the cause and characteristics of ponding along the pipeline.

Growth and yield of Solanum khasianum in Pinus roxburghii forest based silvi-medicinal system in mid hills of Indian Himalaya

Background：In mid hills of Western Himalayas,Himachal Pradesh India,growth,yield and economics of Solanum khasianum as a potential medicinal herb under Pinus roxburghii（Chir pine） plantation has been studied for two consecutive years to assess the performance of Solanum khasianum in undercanopy of Pinus roxburghii for developing Solanum khasianum and Pinus roxburghii based innovative silvi-medicinal system.Methods：Growth parameters such as plant height,number of branches per plant and leaf area index followed by yield were estimated after Solanum khasianum was grown on three topographical aspects as;Northern,North- western and Western at a spacing of 45 cm x 45 cm,followed by three tillage depths as;minimum（0 cm）,medium（up to 10 cm）and deep tillage（up to 15 cm）,in open and below canopy conditions treatment.The study was conducted to explore the possibility of using Solanum khasianum based silvi-medicinal system to utilize the below canopy of Chir pine forest for enhancing the productivity of forests besides the conservation of the medicinal herb.Results：The growth parameters such as plant height,number of branches per plant and leaf area index were nonsignificantly affected by topographical aspects and tillage practices,both below canopy and open conditions except fresh weight and dry weight of berries during harvesting stage.The maximum yield（0.61 t·ha^（-1）） was observed on Western aspect in open conditions as compared to below canopy of Chir pine.The highest gross returns were observed for the crop cultivated on Western aspect under deep tillage in open conditions than other aspect and tillage combinations.However the positive net returns from the crops raised in below canopy of Chir pine indicates its possible economic viability under agroforestry system as the gross returns was higher than the cost of cultivation.Conclusion：Solanum khasianum when grown in below canopy of Pinus roxburghii,its growth and yield indicated positive net returns.Solanum khasianum and Pinus roxburghii based silvi-medicinal system has the potential to enhance the overall productivity of Chir pine forest.This silvi-medicinal system gives scope for utilizing floor Chir pine forests for growth and production of Solanum khasianum beside conservation of the medicinal herb.