Studies Of Small Watersheds Research Articles

Nonpoint Source Pollution in Plot-Scale and Small Watershed Studies under Natural Rainfall: An Analysis of the China Experience

Agricultural nonpoint source (NPS) pollution is still the main factor that affects the quality of rivers, lakes, and reservoirs. Starting from the study of the mechanism of NPS, taking the Yangliu small watershed in the Shaanxi section of the Hanjiang River Basin in China as an example, and based on the combination of measured data and models, this paper focused on the analysis of the characteristics of NPS between the runoff plot and small watershed. The results showed that with the rainfall and surface runoff, the nutrient concentration increased first and then decreased, and the highest occurred in the first half of the whole rainfall process. Rainfall, maximum rainfall intensity at 60 min (I60), runoff, and suspended sediment (SS) were all related to nutrient diversion loss. However, the correlation among rainfall, I60, and runoff and the content of various forms of nitrogen and phosphorus were significantly higher than that of SS. Crop interplanting and terrace planting could play a significant role in reducing sediment and nutrient loss. For the analysis of NPS pollution in small watersheds, the time-variant gain model (TVGM) was used to simulate the missing flow in some months of the basin during the flood season. The average concentration method was used to calculate the NPS pollution load in flood season. It was found that total nitrogen (TN) and total phosphorus (TP) accounted for more than 92% and 69%, respectively. This study is expected to provide scientific basis for NPS pollution control in areas both regionally and worldwide.

Experimental determination of the time of concentration, Sapucajuba creek small watershed study

Time of concentration (tc) is a parameter that indicates the response time of a river catchment to a rainfall. Frequently, empirical equations are used to determination of tc for the design of the maximum flow. However, the determination of this response time by equations sometimes results in an erroneous application, that is, outside its field of validity. Thus, the present work aimed to determine tc in an experimental and simplified way in the Sapucajuba creek, from measurements in the field, with saline tracer, and to make a comparison with 13 empirical models, which require the morphometric characteristics of the small watershed. It was observed that they underestimated the time of concentration value, in general, by empirical models, overestimating the future project flow. DNOS (sandy-clay condition, intense vegetation, high absorption) was the most indicated model for the estimate of tc, that provided the lowest percentage error, 1.92%, compared to tc measured in the field. However, such error exceeded 70.00% by other models, showing great variability. Therefore, it is strongly recommended the determination of tc in field, that will provide a real result, contributing to the economic dimensioning of hydraulic-hydrological works and projects.

Severe western Canadian wildfire affects water quality even at large basin scales

Wildfires can have severe and lasting impacts on the water quality of aquatic ecosystems. However, our understanding of these impacts is founded primarily from studies of small watersheds with well-connected runoff regimes. Despite the predominance of large, low-relief rivers across the fire-prone Boreal forest, it is unclear to what extent and duration wildfire-related material (e.g., ash) can be observed within these systems that typically buffer upstream disturbance signals. Following the devastating 2016 Fort McMurray wildfire in western Canada, we initiated a multi-faceted water quality monitoring program that suggested brief (hours to days) wildfire signatures could be detected in several large river systems, particularly following rainfall events greater than 10 mm. Continuous monitoring of flow and water quality showed distinct, precipitation-associated signatures of ash transport in rivers draining expansive (800–100,000 km2) and partially-burned (<1–22 percent burned) watersheds, which were not evident in nearby unburned regions. Yields of suspended sediment, nutrients (nitrogen, phosphorus) and metals (lead, others) from impacted rivers were 1.2–10 times greater than from those draining unburned regions. Post-fire suspended sediment concentrations in impacted rivers were often larger than pre-fire 95% prediction intervals based on several years of water sampling. These multiple lines of evidence indicate that low-relief landscapes can mobilize wildfire-related material to rivers similarly, though less-intensively and over shorter durations, than headwater regions. We propose that uneven mixing of heavily-impacted tributaries with high-order rivers may partially explain detection of wildfire signals in these large systems that may impact downstream water users.

Ichthyofauna of streams of the Lower Paranapanema River basin, state of Paraná, Brazil

Several studies of small watersheds of in the Upper Paraná River basin are currently available. Howev-er, the number and extent of its tributary streams still pose a challenge to enhancing current knowledge of their ichthyofauna. This study aimed to survey the fish fauna of three streams of the Lower Paranapanema River basin, state of Paraná, Brazil (Capim, Tenente and Centenário streams). The sampling included 3,167 specimens belonging to five orders, 17 families and 56 species. The streams presented differences in species richness (Centenário Stream: 41 species; Tenente Stream: 33 species; Capim Stream: 30 species). Two species occurred at all collection sites (Astyanax bockmanni and Hypostomus ancistroides). Nine non-native species were recorded, four of them found exclusive-ly in the Centenário Stream.

Deep groundwater flow as the main pathway for chemical outputs in a small headwater watershed (Mule Hole, South India)

This study examined the water and chemical cycles of a small forested head catchment. Application of Cl− mass balance lead to the identification of a groundwater baseflow located into the active zone of the crystalline aquifer, below the weir. These findings indicate that groundwater contributes to a large part of chemical outputs at the catchment scale. This study shows that groundwater should not be ignored in most small watershed studies because this flow path and associated solutes are strongly significant for chemical balance assessment.

Determining Effective Impervious Area for Urban Hydrologic Modeling

This paper presents a two-step process to estimate the fraction of an urban watershed covered by a hydraulically effective impervious area. The first step applies maximum likelihood classification of fine-scale multispectral satellite imagery to derive urban land cover. The second step uses an automated macro in a geographic information system to trace the water flow path from pixels classified as impervious and subclassify them as noneffective or effective. The two steps were verified independently, with verification of the second step using idealized data. The two-step process was then tested with a small watershed study of model calibration and rooftop connectivity impact on runoff. At the watershed scale the land cover classification differences were approximately 6%, while at the pixel scale matches of 50, 60, and 83% were achieved for the rooftop, asphalt/concrete, and vegetation land covers, respectively. The effective impervious area was estimated to comprise 16% of the watershed surface, which was close to the actual value of 22%. At the pixel scale, the effective impervious area match was less accurate at 48%. Differences in both land cover and effective impervious area classification at all scales are attributed to high land surface heterogeneity, data limitations and errors, and tree canopy covering impervious surfaces. The verification tests and runoff simulations validate the method as a useful means to rapidly estimate with reasonable accuracy an essential urban hydrologic model parameter.

Solute geochemical mass-balances and mineral weathering rates in small watersheds: Methodology, recent advances, and future directions

Solute-based geochemical mass balance methods are commonly used in small-watershed studies to estimate rates of a variety of geochemical processes at the Earth’s surface, including primary-mineral weathering and soil formation, and the quantitative contribution of these elemental transfer processes to cation budgets, nutrient cycling, and landscape susceptibility to acid deposition. Weathering rates of individual minerals in watershed mass-balance studies are determined by solving a system of simultaneous linear geochemical mass-balance equations with constant (stoichiometric) coefficients. These equations relate the measured net fluxes to the (known) stoichiometries and (unknown) rates of weathering reactions for multiple minerals in the weathering profiles. Solving the system of equations requires petrologic, mineralogic, hydrologic, botanical, and aqueous geochemical data. The number of mineral-weathering rates that can be determined is limited by the number of elements for which solute mass-balance equations can be written. In addition to calculating mineral weathering rates, elemental transfer into or out of the biomass may also be calculated. Elemental uptake by aggrading forest vegetation can act as an intrawatershed sink for at least some mineral-derived cations, producing mineral weathering rates higher than would be estimated from solute fluxes alone; similarly, element release from decaying forest biomass can result in higher solute fluxes than are produced by weathering alone. The mathematics of, significant contributions from, role of biomass in, and recent advances in, watershed geochemical mass-balance methods are discussed using examples from the Appalachian headwaters watersheds of the Coweeta Hydrologic Laboratory in the southern Blue Ridge Physiographic Province of North Carolina, USA.

Reply to comment on ‘Characterization of surface and ground water δ18O seasonal variation and its use for estimating groundwater residence times’ by R. E. Criss and W. E. Winston

It is the nature of the scientific method to use a variety of models, procedures, techniques and data to quantify and analyse natural phenomena. Recently, in Reddy et al. (2006), we published a study in which υ18O values for precipitation, surfaceand ground-water samples from the Shingobee River Headwaters Area (SRHA) were analysed using an amplitude-attenuation (convolution integral) approach for estimating mean residence times (MRTs). This approach has been used in many small watershed studies (e.g. Stewart and McDonnell, 1991; DeWalle et al., 1997; Burns and McDonnell, 1998; McGuire et al., 2002; Rodgers et al., 2005; McGuire and McDonnell, 2006). In a comment, Criss and Winston (2006) disagree with our method and present an alternative approach for interpreting υ18O values in the SRHA. We feel that this comparison with our methodology is unfair. Criss and Winston (2006) focus their attention on the weaknesses in our method and the strengths of theirs, while overlooking our detailed evaluation of model predictions with other independent watershed hydrologic properties. The comment by Criss and Winston (2006) makes several points, some of which we agree are valid criticisms of our paper. In this response, we will address their concerns regarding (1) our interpretation of the current state of the literature, (2) the data we used in the analysis, and (3) the relative merits of the two modelling approaches. In so doing, we will update the dataset with precipitation υ18O data from 1990 to 2004, and compare the two approaches to provide a fair basis for understanding the strengths and weaknesses of both methods. Additionally, we will discuss some technical issues that arise for scientists in choosing between simple and complex models.

Hydrological and biogeochemical processes in a changing Amazon: results from small watershed studies and the large‐scale biosphere‐atmosphere experiment

AbstractThe Amazon Basin is the world's largest tropical forest region and one where rapid human changes to land cover have the potential to cause significant changes to hydrological and biogeochemical processes. The Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA) is a multidisciplinary, multinational research program led by Brazil. The goal of LBA is to understand how the Amazon Basin functions as a regional entity in the earth system and how these functions are changing as a result of ongoing human activity. This compilation of nine papers focuses on a central LBA question in the area of nutrient dynamics and surface water chemistry—how do changes in land use alter fluxes of dissolved and particulate materials from uplands across riparian zones and down the channels of river corridors? These papers cover work conducted in small watersheds on a wide range of topics within the spirit and geographical focus area of LBA: water balance and runoff generation, nutrient transformations in riparian zones and stream channels, carbon fluxes in water moving from land to water and the influence of soils on flowpath structure and stream chemistry. Important new insights can be gained from these and other studies. Forest clearing for pastures results in a decrease in soil hydraulic conductivity that forces water into surficial flowpaths throughout most of the rainy season across wide regions of the Amazon. Riparian zones along small forest streams appear to be very effective in removing nitrate arriving from the uplands, while forest streams take up nitrate at very low rates, allowing them to travel downstream for long distances. Although substantial, the contribution of dissolved organic C (DOC) to the carbon flux from forests to streams appears to be lower than the flux of dissolved inorganic C that is subsequently outgassed as CO2. Remaining key challenges within LBA will be to synthesize existing data sets on river networks, soils, climate, land use and planned infrastructure for the Amazon to develop models capable of predicting hydrologic and biogeochemical fluxes at a variety of scales relevant to the development of strategies for sustainable management of the Amazon's remarkable forest, soil and freshwater resources. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Current awareness

Hydrological ProcessesVolume 20, Issue 12 p. i-iii Current Awareness Current awareness First published: 24 July 2006 https://doi.org/10.1002/hyp.6305AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue12Special Issue: Hydrological and biogeochemical processes in a changing Amazon: Results from small watershed studies and the large scale biosphere-atmosphere experiment15 August 2006Pages i-iii RelatedInformation

The Significance of Ground Water in Small Watershed Studies

The Significance of Ground Water in Small Watershed Studies

Hydrogeochemical controls on the variations in chemical characteristics of natural organic matter at a small freshwater wetland

This study investigated the spatiotemporal variability in dissolved organic carbon concentration ([DOC]), natural organic matter (NOM) weight average molecular weight ( M w), and absorptivity at 280 nm ( ε 280, an estimator of aromaticity) at McDonalds Branch, a first-order stream that is a fen wetland. When ground-water discharge to the stream was predominant, the [DOC], M w, and ε 280 were all relatively low. When soil pore water represented an important contribution to streamflow, not only was the [DOC] higher, but also the M w and ε 280. Hence, the contribution of soil pore water relative to ground water controlled not only the concentration but also the average physicochemical characteristics of the NOM. Combined field and laboratory experiments suggested that preferential adsorption of higher M w, more aromatic NOM components to mineral surfaces, most likely within the lower soil horizons, resulted in a lower M w, more aliphatic ground-water NOM pool. This process ultimately affected surface water as ground water discharged to the lower reaches of the stream. Within the stream, higher molecular weight, more aromatic components were susceptible to photo-aggregation and photo-degradation, in the presence of Fe. Results from this small watershed study provide insight into climatic effects on surface-water NOM characteristics in a small freshwater fen. Low flow periods resulted in lower M w, more aliphatic NOM derived primarily from ground-water discharge to the stream, whereas higher flow periods resulted in a higher M w (by 150–500 Da, i.e., increased by as much as 25%), more aromatic downstream surface-water NOM pool. Hence, during future summer drought periods, as suggested by climate-change models for much of North America, surface-water NOM likely will be lower molecular weight, more aliphatic, and more hydrophilic with lesser metal binding and hydrophobic organic carbon (HOC) uptake abilities [Environ. Sci. Technol. 34 (2000) 1103], along with decreased ability to attenuate UV radiation. Because NOM plays an important role in attenuating UV radiation, research on climate-induced effects on aquatic ecosystems needs to consider not only decreases in NOM concentration and photochemistry but also hydrology-induced changes to the NOM physicochemical characteristics.

Geochemical mass balances and weathering rates in forested watersheds of the southern Blue Ridge II. Effects of botanical uptake terms

Geochemical mass balance methods are commonly used in small-watershed studies to estimate rates of primary-mineral weathering and soil formation, and the contribution of these processes to cation budgets, nutrient cycling, and landscape susceptibility to acid deposition. Many researchers employ the “balance sheet” approach, a system of simultaneous linear equations with constant coefficients which represent the steady-state behavior of the modelled system. Most workers also assume that the steady-state assumption for the entire system means that botanical factors can be ignored; in other words, that there is no net elemental transfer between biomass and inorganic compartments of the system. However, the widely invoked assumption that biomass is at steady-state is mathematically a second, explicit assumption, not a built-in mathematical consequence of the assumption of overall steady-state. The common assumption that the biomass is necessarily at steady-state in a steady-state system ignores the possibility of uptake of elements into the forest biomass. To quantify the implications of the separate mathematical assumptions, weathering rates for seven forested watersheds in the southern Blue Ridge mountains are calculated twice, once allowing for net element exchange with biomass, and once assuming no net exchange with biomass. Our calculations show that misunderstanding the mathematical constraints which are built into the most widely used geochemical mass balance equations commonly causes errors (underestimates) of up to a factor of 4 in the calculated rates of mineral weathering and soil formation. This problem is most pronounced for minerals which contain major nutrient elements, and for rates calculated from mass balances of those nutrient elements.

Forest Harvest and Site Preparation Effects on Stormflow and Peakflow of Ephemeral Streams in the Ouachita Mountains

AbstractStormflow and peakflow response to three silvicultural treatments—clearcutting, selection cutting and no disturbance (control)—were compared in a replicated small watershed study in the Ouachita Mountains of Arkansas. Watersheds were blocked according to aspect, location, soils, and geology in a randomized complete block design to test effects of treatments. Soils on the watersheds are shallow and were derived from sandstones and shale parent materials. Annual precipitation totals ranged from 72 to 142% of the long‐term average (131.7 cm) during the study and a single rainstorm exceeding the 100‐yr, 24‐h event occurred the second year following harvest treatments. Overall, stormflow water yields did not increase significantly due to forest harvest treatments apparently because permeable soils and subsurface geology allowed deep seepage at the expense of Stormflow. However, a treatment response was observed within one block and there was clearly a difference in Stormflow response between blocks of watersheds. Annual stormflow as a percentage of precipitation ranged from 2 to 59% across watersheds and years. Overall peakflows did not increase significantly due to treatment, but a treatment response was obseved within one block of watersheds and there was a significant difference in peakflows between blocks. Treatment differences in Stormflow and peakflow for the 100‐yr event were not significant. Stormflow to precipitation ratios for this event ranged from 0.63 to 0.81.

Forest Harvest and Site Preparation Effects on Erosion and Sedimentation in the Ouachita Mountains

AbstractSoil erosion and sedimentation effects of three silvicultural treatments—clearcutting, selection cutting and no disturbance (control)—were compared in a replicated small watershed study conducted in the Ouachita Mountains of Arkansas on shallow soils derived from sandstones and shales. Clearcutting significantly increased annual sediment yields over selection and control treatments in 1981, the first year, after treatment but not in 1982 or 1983. Clearcut to control sediment yield ratios were 20:1, 6:1, and 2.6:1 in 1981, 1982, and 1983, respectively. First‐year sediment losses from clearcuts averaged 237 kg ha−1. Stream channels were stable, but they still may have been the primary source of the sediment losses. Erosion following harvest and site preparation did not exceed estimates of long‐term soil formation rates. Longterm soil losses were projected to average 70 kg ha−1 yr−1 over a 35‐yr rotation period with clearcutting while control rates were projected to average 50 kg ha−1 yr−1. A comparison of soil losses measured in this study with baseline rates and estimated soil loss tolerances suggests site productivity need not be threatened by silviculturally induced soil erosion. Suspended solids levels of stormflow were less than 100, 50, and 20 mg L−1 at least 99, 98, and 97% of the time, respectively, across treatments. Only at the 10 mg L−1 level was there a significant total suspended solids time differential in watershed stormflow between clearcut or selection cut and control treatments.

Book reviews

Abstract Book reviewed in this article: Qualities of Communities Life. Roger G. Barker and Phil Schoggen. Topophilia: A Study of Environmental Perception, Attitudes and Values. Yi-Fu Tuan. The Linguistic Atlas of the Upper Midwest. Volume 1. Harolad B. Allen. Residential and Neighbourhood Studies in Victoria. C. N. Forward (Ed.). Social Patterns in Cities. Compiled by B. D. Clark and M. B. Gleave. Community Participation and the Spatial Order of the City. David Ley (Ed.). Red Capitalism: An Analysis of the Navajo Economy. Kent Gilbreath. Regional Growth and Industrial Location. Leonard F. Wheat. Transport for the Space Economy; A Geographical Study. Allan Hay. Geographie des Transports. Maurice Wolkowitsch. Urban and Regional Models in Geography and Planning. A. G. Wilson. Location Criteria for High Schools. Fred L. Hall. Space-Time Concepts in Urban and Regional Models. E. L. Cripps (Ed.). Fluvial Processes in Instrumental Watersheds: Studies of Small Watersheds in the British Isles. K. J. Gregory and D. E. Walling (Eds.). One-Dimensional Central Place Theory. M. F. Dacey, O. Davies, R. Flowerdew, J. Huff, A. Ko, and J. Pipkin. Developments in Geographical Method; Data Collection; Data Description and Presentation; and Data Use and Interpretation. Brian P. FitzGerald, Richard Daugherty, Peter Davis, and Patrick McCullagh. Quantitative Techniques in Geography: An Introduction. R. Hammond and P. S. McCullagh. An Introduction to Quantitative Analysis in Human Geography. Maurice Yeates. Primary Producers in Grassland Ecosystems. James K. Lewis.

Report of the Committee on Runoff, 1955–1956

During the year 1955–1956 the Committee on Runoff conducted several informal discussions by correspondence on subjects of runoff from small watersheds and of flood and drought studies. Owing to the limitation in space for publication, voluminous material involved in the discussiong cannot be all published. This report presents some highlights developed from discussions on runoff studies of small watersheds. The report constitutes neither recommendations nor complete opinions on the part of the Committee members, but simply reflects some fragmental thoughts that have been expressed during the discussions. The Committee members hope that this report will serve as seeds to bring forth further discussions from the readers and thus to fulfill the aim to stimulate research, secure coordination, and facilitate dissemination of information in runoff studies of small watersheds.

Extension of graphic methods of analysis of sprinkled‐plots hydrographs to the analysis of hydrographs of control‐plots Small Homogeneous watersheds

The development of the plans of Infiltration Studies (under the direction of G. W. MUSGRAVE, Office of Research, Soil Conservation Service, United States Department of Agriculture, Washington, D.C., and with the cooperation of the Hydrologic Division, same office) to make simultaneous studies of small watersheds by means of infiltrometers and small control‐plots, and the watersheds as a whole, has made it desirable, even necessary, to develop more precise methods of analyzing hydrographs of such control‐plots and the small watersheds. Following is a proposed method of extending and adapting the graphic method of analyzing sprinkled‐plot hydrographs developed by the authors for this purpose [see 3 of “References” at end of paper].