Flat Watersheds Research Articles

Перспективы Крайнего Северо-Востока России на производство "зеленого" водорода с использованием климатических источников возобновляемой энергии

For the first time, Russia's Far North-East prospects for hydrogen production by the method of water electrolysis, using climatic energy sources and ultra-fresh mountain-river water, are comprehensively assessed. Taking into account the identified regional features, it is calculated that, with the current technical level of development, the amount of hydrogen produced in the region will be controlled just by the amount of used ultra-fresh mountain-river water. Thus, using no more than 10 percent of the general runoff (18 billion m3 water), it is possible to annually obtain 2x109 tons of "green" hydrogen through the operation of wind and solar power plants. To accommodate the latter, it is ecologically feasible to use the areas in mountain tundras and forest-tundras on flattened and flat watersheds.

Effects of digital elevation model data source on HSPF-based watershed-scale flow and water quality simulations.

Digital elevation models (DEMs) from different sources have been widely utilized in watershed modeling and environment management. Yet, little is known about how DEMs from different data sources affect modeling results and management decisions. This paper presents new insights into how the DEMs from three different sources affect model-simulated flow, nitrate (NO3), phosphorus (P), and sediment by using the BASINS/HSPF watershed modeling system. It was found that DEM source-induced uncertainties in simulation results are higher than the DEM resolution-induced uncertainties regardless of watershed slope or delineation method. Moreover, DEM source introduces higher uncertainties in simulation results for automatically delineated low-gradient watersheds than high gradient watersheds. Sediment and NO3 concentrations were the most and the least sensitive water quality parameters, respectively, to DEM sources. The uncertainties in simulation results may be reduced by using the manual method for watershed delineation but they cannot be completely eliminated. It is recommended that high precision (such as NED) DEMs be employed especially for flat watersheds. The findings provide guidelines for selection of DEM source based on available resources.

Dynamics of peat accumulation processes in the areas of the periglacial zone of the basin watershed of Tugur-Nimelen rivers

The paper considers the features of waterlogging of a flat watershed, unique in its structure and evolution, between the valley complexes of the two largest watercourses of Khabarovsk Territory. The Tugur and Nimelen rivers had rather powerful debit of water flows during the Pleistocene and were repeatedly redirected from the northern azimuth (the Sea of Okhotsk) to the southern one (the Amur catchment). This process continued partly at the early stages of the Holocene, as the stratigraphy of the peat deposits of the bogs formed indicates here.

Landscape differentiation of the territory of the Sergachsky district of the Nizhny Novgorod region (Russia)

The territory of the Sergachsky district of the Nizhny Novgorod region is located in the north of the forest-steppe zone, at the northern extremity of the Privolzhskaya Upland. Due to favorable agroclimatic conditions, the researched territory is characterized by a high degree of anthropogenic transformation of landscapes, mainly involved in agriculture. Areas of broad-leaved forests have been preserved mainly in places, that are inconvenient for plowing – on the steep slopes of river valleys and in ravines. Flat watersheds and sloping slopes have been plowing for several centuries. Thus, the landscape features of the territory traditionally determined the type of economic activity and its territorial boundaries, but often land use planning was carried out on an intuitive level, based on the experience of life in the landscape, but not on a systematic account of the specifics of its components. The long-standing and intensive economic pressure has led to a reduction in forest cover, a decrease in biodiversity, the development of erosion processes, and the degradation of soil cover. Further development of the economy in the researched area requires the adoption of well-thought-out decisions, based on the results of geosystem analysis. During solving problems of territorial planning, nature management, implementation of environmental protection measures, the most effective is the use of a landscape approach. However, until the present, the scheme of landscape differentiation of the territory of the Sergachsky district at the hierarchical level of landscapes has not been developed. The article presents the results of landscape zoning of the territory of the Sergachsky district of the Nizhny Novgorod region, performed on the basis of field research, analysis of maps, literature sources and remote sensing data processed using GIS. The presented results are the basis for making management decisions in the researched area.

Influence of different relief information sources on the geomorphological characterization of small watersheds.

Mathematical models have been widely used to quantify hydrological processes for various practical purposes. These models depend on geomorphological attributes which are derived from relief information represented by Digital Elevation Models (DEM). The objective of this study was to evaluate the influence of relief information sources (ASTER, SRTM-30, SRTM-90, and TOPO) over geomorphological characterization of five Brazilian watersheds. Geoprocessing tools were applied for extraction of the following geomorphological attributes for each DEM: drainage area, perimeter, and watershed slope; length and slope of the main stream; total length of streams; bifurcation, stream length and stream area ratios; and length of the highest order stream. The differences in the values of attributes were calculated in relation to the reference DEM (TOPO). It was found that: i) slope of main stream and bifurcation ratio were the most sensitive parameters regarding the relief information source; ii) flat watersheds were more susceptible to altimetric errors; iii) ASTER did not adequately represent drainage networks for flat watersheds; and iv) the differences in the geomorphological attributes increased as drainage area decreased. The results indicate that DEM may exert influence on the use of hydrological models that depend on geomorphological attributes.

The Interactive Impact of Land Cover and DEM Resolution on the Accuracy of Computed Streamflow Using the SWAT Model

Twenty daily time step–based SWAT simulation models for the Duhok, Adhaim and Dokan dam watersheds, in Iraq, were implemented using five land cover (LC) and digital elevation model (DEM) of different resolutions. The optimal LC and DEM for computing the most accurate streamflow for each watershed were specified. Results indicated that delineation of the flat watersheds is significantly affected by the DEM resolution and there was no evident trend on the computation of watersheds’ total areas, boundaries, number of subbasins and stream networks. Moreover, there is no significant trend between the increase in LC and DEM resolutions and accuracy of the computed streamflow. The most accurate streamflows for the Duhok, Adhaim and Dokan watersheds were computed using LC (DEM) of 30 m, 1000 m and 1000 m.

Soil cover of the Fildes Peninsula (King George Island, West Antarctica)

Data on the morphology and major physical and chemical properties of 130 pedons sampled in the ice-free area of the Fildes Peninsula and adjacent Ardley Island (King George Island, West Antarctica) are analyzed, and the soil-geomorphological map of the surveyed area on the scale of 1:10 000 is presented. The soils have been classified according to the WRB (2014/2015) system. The map provides information on the soil cover patterns in relation to geomorphic elements and also reflects the degree of anthropogenic load on the studied territory. Nearly half (42.9%) of the total area is covered by different subgroups of Cryosols. Flat watersheds are mainly occupied by Protic Arenosols (Turbic) (22.9%). Leptosols are mainly represented by the Lithic (Ochric) subgroup covering 13.8% of the area. Fluvisols are locally developed in the tidal zone (3.3% of the total area) and are represented by the Tidalic (Skeletic) subgroup. The unique area of Fibric Cryic Histosol (0.02%) is separately delineated. Various Hyperskeletic Technosols (Toxic, Transportic, and Urbic) are formed under the influence of human loads and cover about 0.9% of the Fildes Peninsula and Ardley Island. The map as the main result of the study can be used for monitoring and forecasting the environmental changes of soil cover pattern under the global climate change and local anthropogenic impact.

Low snowpack reduces thermal response diversity among streams across a landscape

AbstractSpatial and temporal variation in thermal conditions are important dimensions of aquatic landscapes, yet we do not understand how this heterogeneity will respond to climate change. Snowpack in many regions is declining but impacts on aquatic thermal regimes remain poorly understood. Our analyses of summer stream temperatures across a complex river basin in southwest Alaska show that loss of snowpack has disproportionate effects on water temperatures in streams that are cold under typical conditions, thereby homogenizing stream temperatures across the landscape during low snow conditions. Streams draining steep watersheds warmed from a summer average of 4–8°C between high and low snow years and became more responsive to variation in regional air temperature (as proxy for solar radiation), while streams draining flat watersheds changed negligibly. Our results suggest that conservation strategies for aquatic landscapes that focus on snow‐dominated cold‐water refugia may not be robust to future climate warming and changes in snowpack.

Watershed geomorphology modifies the sensitivity of aquatic ecosystem metabolism to temperature

The regulation of aquatic carbon cycles by temperature is a significant uncertainty in our understanding of how watersheds will respond to climate change. Aquatic ecosystems transport substantial quantities of carbon to the atmosphere and ocean, yet we have limited understanding of how temperature modifies aquatic ecosystem metabolic processes and contributions to carbon cycles at watershed to global scales. We propose that geomorphology controls the distribution and quality of organic material that forms the metabolic base of aquatic ecosystems, thereby controlling the response of aquatic ecosystem metabolism to temperature across landscapes. Across 23 streams and four years during summer baseflow, we estimated variation in the temperature sensitivity of ecosystem respiration (R) among streams draining watersheds with different geomorphic characteristics across a boreal river basin. We found that geomorphic features imposed strong controls on temperature sensitivity; R in streams draining flat watersheds was up to six times more temperature sensitive than streams draining steeper watersheds. Further, our results show that this association between watershed geomorphology and temperature sensitivity of R was linked to the carbon quality of substrates that changed systematically across the geomorphic gradient. This suggests that geomorphology will control how carbon is transported, stored, and incorporated into river food webs as the climate warms.

Растительность среднего течения р. Яхадыяха (южная часть арктических тундр п-ва Ямал)

For the first time a syntaxonomical diversity was determined for the arctic tundra of Yamal. In total, 6 associations, 3 subassociations and 5 communities that belong to 5 classes, 5 orders and 6 alliances were revealed for the northern part of the peninsula. From them, 1 association and 3 subassociations are new. The association Dactylino arcticae–Racomitrietum lanuginosi ass. nova hoc loco was attributed to the alliance Loiseleurio–Diapension, order Rhododendro–Vaccinietalia, and class Loiseleurio–Vaccinietea. The communities are confined to the drained above-floodplain lake terraces and shoulders, the convex parts of slopes with slight inclination. Subassociation Antennario lanatae–Arctoetum alpinae lagotoetosum minoris subass. nova hoc loco was included in the alliance Oxytropido sordidae–Tanacetion bipinnati, order Androsacetalia alpinae, and class Thlaspietea rotundifolii. The coenoses are characteristic for eroded deflation slopes. The soils are weakly developed on sandy ground. Herbs, mosses and lichens predominate in the communities. The subassociations Aulacomnio turgidi–Eriophoretum angustifolii сladonietosum bellidiflorae subass. nova hoc loco and Aulacomnio turgidi–Eriophoretum angustifolii bistortetosum viviparae subass. nova hoc loco were attributed to the alliance Carici concoloris–Aulacomnion turgidi, order Rhododendro–Vaccinietalia, and class Loiseleurio–Vaccinietea. The communities of subassociation Aulacomnio turgidi–Eriophoretum angustifolii сladonietosum bellidiflorae subass. nova hoc loco are the elements of tundra-bog complexes occupying flattened river terraces above floodplain and flat watersheds. The coenoses of subassociation Aulacomnio turgidi–Eriophoretum angustifolii bistortetosum viviparae subass. nova hoc loco are characteristic for flattened parts of watersheds, sometimes with slight inclination, as well as for flat surfaces of river and lake terraces.

Watershed geomorphology interacts with precipitation to influence the magnitude and source of CO2 emissions from Alaskan streams

AbstractBoreal ecosystems contain a large fraction of the world's soil carbon and are warming rapidly, prompting efforts to understand the role of freshwaters in carbon export from these regions. We examined geomorphic controls on the magnitude of stream CO2 emissions and sources of stream dissolved inorganic carbon (DIC) across a heterogeneous river basin in SW Alaska. We found that watershed slope and precipitation interact to control gaseous carbon fluxes from streams, with the highest flux from low‐gradient watersheds following rainstorms. Watershed slope influences C loading and stream CO2 fluxes by controlling carbon accumulation in watersheds and to a lesser extent by determining gas transfer velocity across the stream air‐water interface. Low gas transfer velocity in flat streams offsets some of the effects of higher terrestrial C loading at those sites, resulting in lower than expected vertical CO2 fluxes. While the isotopic composition of stream DIC (Δ14C and δ13C) was highly variable across space and time, shifts toward contemporary, terrestrial sources after precipitation were most pronounced in flat watersheds. At base flow DIC was a mixture of modern and aged sources of biogenic and geologic origin (Δ14C, −198.3‰ to 27.9‰, n = 23). Aged (Δ14C‐depleted) C sources contributed to food webs via a pathway from DIC to algae to invertebrate grazers. We observed coherent changes in stream carbon chemistry after large rainstorms despite considerable physical heterogeneity among watersheds. These patterns provide a way to extrapolate across boreal landscapes by constraining CO2 concentration and flux estimates by local geomorphic features.

Evaluation of remotely sensed data for estimating recharge to an outcrop zone of the Guarani Aquifer System (South America)

The Guarani Aquifer System (GAS) is the largest transboundary groundwater reservoir in South America, yet recharge in the GAS outcrop zones is one of the least known hydrological variables. The objective of this study was to assess the suitability of using remote sensing data in the water-budget equation for estimating recharge inter-annual patterns in a representative GAS outcropping area. Data were obtained from remotely sensed estimates of precipitation (P) and evapotranspiration (ET) using TRMM 3B42 V7 and MOD16, respectively, in the Onca Creek watershed in Brazil over the 2004–2012 period. This is an upland flat watershed (slope steepness <1 %) dominated by sandy soils and representative of the GAS outcrop zones. The remote sensing approach was compared to the water-table fluctuation (WTF) method and another water-budget equation using ground-based measurements. On a monthly basis, the TRMM P estimate showed significant agreement with the ground-based P data (r = 0.93 and RMSE = 41 mm). Mean(±SD) satellite-based recharge (R sat) was 537(±224) mm year−1. Mean ground-based recharge using the water-budget (R gr) and the WTF (R wtf) methods were 469 mm year−1 and 311(±75) mm year−1, respectively. Results show that 440 mm year−1 is a mean (between R sat, R gr and R wtf) recharge for the study area over the 2004–2012 period. The latter mean recharge estimate is about 29 % of the mean historical P (1,514 mm year−1). These results are useful for future studies on assessing recharge in the GAS outcrop zones where data are scarce or nonexistent.

Soils with vertic properties in Kamennaya Steppe

The most spread are soils with vertic properties at the territory of Kamennaya Steppe (Voronezh region, Talovsky district) being confined to four landscape positions within 11 different soil combinations derived from clayey or two-layered heavy loam-clayey parent materials. These soils have developed: (A) on bottoms of deep and closed depressions covered by spotted soil combinations in flat watersheds; (B) on some depression bottoms in spotted combinations without solonetzic soils; (C) in different relief elements occupied by chernozemic hydromorphic solonetz complexes and (D) in concave (in long and cross directions) relief elements in the topolithomosaic composition confined to exposed re-deposition products of Dnieper moraine on the slope of Talovaya narrow. Occupying only 0.2% from the total area of agro-forest landscapes, the vertic soils can account for 0.7% to 15% within a separate soil combination and reveal a great diversity. The latter is associated with vertic properties developed together with features of gleying and quasi-gleying, accumulation of calcium carbonates and, on the contrary, clay illuviation against the background of calcium carbonate leaching, solonetz process, salinization, humus formation and the topsoil eluviations. Such a diversity may be adequately reflected both in the soil classification of Russia and in WRB.

Impact of spatial input data resolution on hydrological and erosion modeling: Recommendations from a global assessment

The need to precisely describe the characteristics of a landscape is well-known in mathematical modeling from different environmental disciplines. Because spatial input data, such as climate, relief and soil maps are costly to obtain, especially when large areas are considered, several research studies have investigated the extent to which the resolution of these can be reduced. Yet, a consensus has not been reached on the question of models’ sensitivity to the whole range of spatial input data and for different environmental conditions. This issue was illustrated with the analysis of existing results from 41 watersheds from 30 research studies using the Soil and Water Assessment Tool (SWAT). Because these studies were not consistent in the type of spatial input data considered and the range of resolutions, an application of SWAT was performed in a flat 2612ha flat watershed of central Iowa (USA) where the sensitivity of runoff (R), NO3–N (N) and sediment (SED) yields was tested for changes in the resolution of all the required spatial input data (digital elevation model: DEM: 20–500m; n=12; number of rain gauge: NRAIN from 1 to 13; n=8; soil map: SOIL: 1/25,000–1/500,000; n=3) and in the number of watershed sub-divisions (NSW from 4 to 115; n=4). At the flat watershed, a Canonical Correlation Analysis with 67.4% of data variance explained by the two first variates, revealed that R and SED predictions were affected, mostly by NSW (r=0.95), followed by SOIL (r=0.18). N loads were the most sensitive to RAIN (r=0.76) and DEM (r=0.41), followed by SOIL (r=0.23) and NSW (r=−0.17). The Kolmogorov–Smirnov statistic (KS), that describes the significance of resolution changes for a considered spatial input data, showed that the model’s sensitivity was greater for SSW below 261ha, for 30<DEM<100m and across the whole range of NRAIN. Finally, the analysis of watersheds with different sizes and environmental conditions revealed that the minimum spatial input data resolution needed, to achieve accurate modeling results can be predicted from watersheds’ terrain declivity and mean annual precipitation. These results are expected to help modelers weight the level of investment to be made in generating spatial input data and in subdividing their watersheds as a function of both watersheds’ environmental conditions and desired level of accuracy in the output variables.

Clay minerals in a denudation-accumulative soil catena

Chernozems and agrochernozems of the Kamennaya Steppe agroforest landscape have a silty clay or clay texture and similar associations of clay minerals. The plow horizons of the agrochernozems on a slope of 2°–3° to the Talovaya Balka have an increased content of the smectite phase (50–70%) compared to the upper horizons of the chernozems on flat watersheds (30–50%) due to the lithological discontinuity of the soil-forming material and the possible total removal of material on the slope by denudation. On slightly eroded areas, the clay minerals display a more intense disturbance of their crystal lattice structures by pedogenetic processes, which increase the degree of disorder in their layers and the accumulation of fine quartz in the clay fraction. In the areas with more significant erosion of the humus horizon, the clay minerals are characterized by their perfect structure and clean reflections, which are indicative of the outcropping of less weathered material from the middle part of the chernozem profile less transformed by pedogenesis.

Phosphorus Transport through Subsurface Drainage and Surface Runoff from a Flat Watershed in East Central Illinois, USA

A long-term water quality monitoring program was established to evaluate the effects of agricultural management practices on water quality in the Little Vermilion River (LVR) watershed, IL. This watershed has intensive random and irregular subsurface drainage systems. The objective of this study was to assess the fate and transport of soluble phosphorus (soluble P) through subsurface drainage and surface runoff. Four sites (sites A, B, C, and E) that had subsurface and surface monitoring programs were selected for this study. Three of the four study sites had corn (Zea mays L.) and soybeans (Glycine max L.) planted in rotations and the other site had seed corn and soybeans. Subsurface drainage and surface runoff across all sites removed an average of 16.1 and 2.6% of rainfall, respectively. Annual flow-weighted soluble P concentrations fluctuated with the precipitation, while concentrations tended to increase with high precipitation coupled with high application rates. The long-term average flow-weighted soluble P concentrations in subsurface flow were 102, 99, 194, and 86 microg L(-1) for sites A, B, C, and E, respectively. In contrast, the long-term average flow-weighted soluble P concentrations in surface runoff were 270, 253, 534, and 572 microg L(-1) for sites As, Bs, Cs, and Es, respectively. These values were substantially greater than the critical values that promote eutrophication. Statistical analysis indicated that the effects of crop, discharge, and the interactions between site and discharge and crop and discharge on soluble P concentrations in subsurface flow were significant (alpha = 0.05). Soluble P mass loads in surface runoff responded to discharge more consistently than in the subsurface flow. Subsurface flow had substantially greater annual average soluble P mass loads than surface runoff due to greater flow volume.

Predicting Water, Sediment and NO3-N Loads under Scenarios of Land-use and Management Practices in a Flat Watershed

Changes in land-use or management practices may affect water outflow, sediment, nutrients and pesticides loads. Thus, there is an increasing demand for quantitative information at the watershed scale that would help decision makers or planners to take appropriate decisions. This paper evaluates by a modeling approach the impact of farming practices and land-use changes on water discharge, sediment and NO3-N loads at the outlet of a 51.29 km2 watershed of central Iowa (Walnut Creek watershed). This intensively farmed (corn-soybean rotation) watershed is characterized by a flat topography with tiles and potholes. Nine scenarios of management practices (nitrogen application rates: increase of current rate by 20, 40%, decrease of current rate by 20, 40 and 60%; no tillage) and land-use changes (from corn-soybean rotation to winter wheat and pasture) were tested over a 30 yr simulated period. The selected model (Soil and Water Assessment Tool, SWAT) was first validated using observed flow, sediment and nutrient loads from 1991 to 1998. Scenarios of N application rates did not affect water and sediment annual budgets but did so for NO3-N loads. Lessening the N rate by 20, 40 and 60% in corn-soybean fields decreased mean NO3-N annual loads by 22, 50 and 95%, respectively, with greatest differences during late spring. On the other hand, increasing input N by 20 and 40% enhanced NO3-N loads by 25 and 49%, respectively. When replacing corn-soybean rotation by winter wheat, NO3-N loads increased in early fall, immediately after harvest. Pasture installation with or without fertilization lessened flow discharge, NO3-N and sediment delivery by 58, 97 and 50%, respectively. No-tillage practices did not significantly affect the water resource and sediment loads. Finally, such realistic predictions of the impact of farming systems scenarios over a long period are discussed regarding environmental processes involved.

DEM AGGREGATION FOR WATERSHED MODELING1

ABSTRACT: The widely available USGS 7.5‐minute Digital Elevation Model (DEM) has a cell size of approximately 30 m × 30 m. This high resolution topographic information is impractical for many applications of distributed hydrologic and water quality models. In this study, cells were aggregated into coarse‐resolution areal units, termed grids, and a method to approximate flow direction for coarse‐resolution grids from 30 m DEM cells was developed. The method considers the flow path defined from the fine‐resolution DEM in determining a grid's flow direction and makes flow directions for grids closely follow the flow pattern suggested by the DEM. The aggregation method was applied to a DEM of Goodwater Creek, a nearly flat watershed that is located in central Missouri. The drainage networks derived for different levels of cell aggregations showed that grid aggregates of the Goodwater Creek watershed provided an adequate representation of the landscape topography.

DEM Based Overland Flow Routing Model

A physically based, distributed rainfall-runoff event model is developed to route overland flows from flat agricultural watersheds. The model works on a cell basis and routes overland flows from one cell to the next following the maximum downslope directions. The model is able to consider spatially-varied data of soils, crops, land slopes, and aspects, which can be extracted from geographic information systems (GIS) and from digital elevation models (DEMs). Because of this feature, the model can be used for evaluating the impacts of agricultural practices on surface runoff. To describe overland flows on flat watersheds, the model uses the diffusion wave approximation of the St. Venant equations for computing the hydrograph. The computation is accomplished using the MacCormack scheme, a second order accurate numerical method. The model was tested against analytic solutions of the kinematic wave equations and was applied to route the overland flows across Goodwater Creek, a USDA research watershed. The model was calibrated using 26 events and verified using 11 events. The results show that the model works well.

Temporal and spatial variability, and the role of dissolved organic carbon (DOC) in methane fluxes from the Sabine River Floodplain (Southeast Texas, U.S.A.)

The Sabine River floodplain, in southeast Texas, U.S.A., is a broad flat watershed which contains a diverse assemblage of blackwater wetland habitats. Methane fluxes were compared across a gradient of three different habitats, within the floodplain, that extended from the outer reaches of the basin to the river proper (i.e., blackgum Nyssa aquatica, cypress Taxodium distichum, and arrowhead Sagittaria spp.), as well as a fourth station (a Spartina marsh) within the Sabine-Neches estuary. Concentrations of dissolved organic carbon (DOC) in the floodplain were very high (15-50 mg/l). Methane emissions were highly variable and ranged from 0.0007 to 1640 mg m -2 d -1 , with the highest rates in July 1993. These highest CH 4 emission rates were observed just after the longest period of flooding (ca. 1 month) at each of the stations. Fluxes were significantly correlated (both positively and negatively) with precipitation (p<0.01) ; natural periods of flooding and drought were primarily responsible for the wide range of emissions. Methane consumption rates had little effect on total emissions because of losses by ebullition and plant-mediated transport mechanisms. Plant-mediated transport accounted for as much as 96% of the total CH 4 emissions at certain stations. Laboratory experiments indicated that UV-B treated humic substances were preferentially utilized by methanogens over untreated humic compounds. Thus, variability of light penetrance across a floodplain may affect the quality and ultimately the availability of DOC to methanogens. Finally, the similarity in peak CH 4 emissions, after a 1 month lag period of flooding, in both agricultural and natural wetlands of southeast Texas, may for the first time demonstrate a similar chronological sequence of microbial reactions for CH 4 production in divergent systems.