Increasing Soil Moisture Content Research Articles

Optimizing Cover Crop Benefits with Diverse Mixtures and an Alternative Termination Method

Previous studies have demonstrated benefits of individual cover crop species, but the value of diverse cover crop mixtures has received less attention. The objectives of this research were to determine the effects of spring‐sown cover crop mixture diversity and mechanical cover crop termination method on cover crop and/or cash crop productivity, soil moisture and N, and profitability in an organic cropping system. An experiment was conducted between 2009 and 2011 near Mead, NE, where mixtures of two (2CC), four (4CC), six (6CC), and eight (8CC) cover crop species, or a summer annual weed mixture were included in a sunflower–soybean–corn rotation. Cover crops were terminated in late May using a field disk or sweep plow undercutter. Undercutting cover crops increased soil NO3–N (0–20 cm) by 1.0 and 1.8 mg NO3–N kg−1 relative to disk incorporation in 2010 and 2011, respectively. Cover crop mixtures often reduced soil moisture (0–8 cm) before main crop planting, though cover crop termination with the undercutter increased soil moisture content by as much as 0.024 cm3 cm−3 compared to termination with the disk during early main crop growth. Crop yields were not influenced by cover crop mixture, but termination with the undercutter increased corn and soybean yield by as much as 1.40 and 0.88 Mg ha−1, respectively. Despite differences in productivity between spring cover crop mixtures and weed communities, crop yield was not different among these treatments; thus, profitability of the weed mixture–undercutter treatment combination was greatest due to reduced input costs.

Spatial variation of denitrification potential of grassland, windbreak forest, and riparian forest soils in an agricultural catchment in eastern Hokkaido, Japan

Riparian forest soils have a high denitrification potential (DP), but the effect of their spatial distribution on DP within a catchment has rarely been assessed. To provide insights into this effect, we evaluated the spatial distribution of DP and its control factors in the Shibetsu River Catchment (SRC), eastern Hokkaido, Japan. Soil samples from August 2008 were used in the lab to determine the DP (using the acetylene inhibition method) of grassland, windbreak forest, and riparian forest soils in the SRC. Soil DP ranged from 0.001 to 64mgNkgsoil−1d−1 and followed a log-normal distribution. Soil DP was highest in the surface peat soil of a low-elevation riparian forest. The land-use type and soil depth both significantly affected soil DP, with higher DP in riparian forests and surface soils. Soil DP increased with increasing soil moisture content and water-extractable soil organic carbon (WESOC). The clay, moisture, and WESOC contents in the surface soils decreased significantly with increasing elevation, resulting in increased soil DP in low-elevation riparian forests. The stream NO3− concentration was significantly correlated with the upland (grassland and cropland) proportion (%) of the catchment's area, and the ratio of stream NO3− concentration to this proportion tended to be lower in low-elevation areas, indicating higher NO3− denitrification. We conclude that low-elevation riparian forest soils have a higher DP due to the higher moisture, clay, and WESOC contents of their soils, and that these factors control riverine NO3− export in the SRC.

Effects of Water-Collecting and -Retaining Techniques on Photosynthetic Rates, Yield, and Water Use Efficiency of Millet Grown in a Semiarid Region

Field experiments were conducted in 2003 and 2004 to study the effects of plastic ridges and furrow film mulching (plastic film on sowing, as well as plastic film on flat soil and hole sowing) and chemicals (a drought resistant agent and a water-retaining agent) on growth, photosynthetic rate, yield, and water use efficiency (WUE) of spring millet (Setaria italica L.). The experimental results showed that water-collecting and -retaining techniques can effectively increase soil moisture content, the leaf photosynthetic rate and crop growth. Due to increased soil moisture under the plastic-covered ridge and furrow water-collecting in July and August, dry matter and plant height had a increase at the booting stage (late growth advantage). However, the plastic-covered flat soil and hole sowing reduced soil evaporation during early growth, the increase of dry matter and plant height appeared at the seedling stage (early growth advantage). Plastic-covered ridge and furrow sowing supplemented with chemical reagents had significant positive effects on water collection and soil moisture retention. Improvement of soil moisture resulted into the increase of the photosynthetic rate, dry matter accumulation yield and WUE. The water-collecting and -retaining techniques can improve WUE and enhance crop yield. Correlation analysis demonstrated that the photosynthetic rate under the water-collecting and -retaining techniques was significantly associated with the soil moisture, but had no significant relationship with leaf chlorophyll content. Plastic-covered ridge and furrow sowing supplemented with chemical reagents increased the yield and WUE by 114% and 8.16 kg ha−1 mm−1, respectively, compared with the control; while without the chemical reagents the yield and WUE were 95% and 7.42 kg ha−1 mm−1 higher, respectively, than those of the control.

A Participatory GIS Approach for Assessing Land Suitability for Rainwater Harvesting in an Arid Rangeland Environment

The dry rangelands of West Asia and North Africa are fragile and severely degraded due to low rainfall and mismanagement of natural resources. Rainwater harvesting (RWH) interventions are used to increase soil moisture content, vegetation cover, and productivity. However, adoption of rainwater harvesting by communities is slow. To understand adoption constraints and to develop options for sustainable integration of rainwater harvesting, a benchmark watershed was established in the dry rangelands of Jordan. The objective is to develop a methodology for identifying the suitability for different rainwater harvesting interventions using participatory GIS approach and field survey. The main biophysical parameters used to assess the suitability for rainwater harvesting were slope, soil depth, soil texture, and stoniness. Criteria for each parameter were integrated and a suitability map was produced using raster-based and polygon-based analysis. To integrate biophysical and socio-economic aspects, the land tenure was superimposed with the suitability map. Options for implementing different rainwater harvesting interventions were identified with the participation of the local communities. Field investigations indicated that the applied approach helped to select the most promising fields. Within two years, four types of rainwater harvesting were implemented in the fields of 41 farmers, covering 62.9 hectares, which helped to increase water productivity (kg/m3) four folds and reducing soil erosion five folds compared to fields without rainwater harvesting. The approach showed that participatory GIS approach may be used to integrate socio-economic and biophysical criteria and facilitate the participation of farmers to introduce rainwater harvesting interventions in dry rangeland systems to mitigate land degradation.

녹비작물 도입에 따른 토마토 시설재배지 연작장해 토양 개량 효과

Four different green manure crops, hairy vetch, Italian ryegrass, crimson clover, orchard grass were cultivated to test the differences in their effects on soil improvement. After plowing to incorporate the green manure crops, tomato plants were grown as a succeeding crop to investigate the effects of green manure on the soil physical properties and plant growths. The experimental results showed that green manure could decrease the soil hardness. Italian ryegrass and hairy vetch as the green manure were especially effective in decreasing the soil hardness. Orchard grass and Italian ryegrass provided more void in soil matrix, resulting increased soil moisture contents. After two months, bulk density was decreased in the plots of Italian ryegrass and orchard grass. However, there were no significant differences between green manure plots and control after the cultivation of the succeeding crop. The results indicated that the growing Italian ryegrass and hairy vetch as green manure helped growing tomato plants. Orchard grass also improved the soil characteristics, comparable to Italian ryegrass in spite of their relatively small biomass.

Effects of diatomite on soil physical properties

Abstract Organic and inorganic soil amendments are commonly added to soil for improving its physical and chemical characteristics which promote plant growth. Although many inorganic amendments are extensively used for this purpose, diatomite (DE) is not commonly used. This study was conducted to determine effects of diatomite applications (10, 20, and 30% v/v) on physical characteristics of soils with different textures (Sandy Loam, Loam, and Clay), under laboratory conditions. The results indicated that diatomite application protects large aggregate (> 6.4 mm) formation in clay-textured soils, however it reduced the mean weight diameter in sand-textured soil. 30% diatomite reduced mean weight diameter in sand-textured soils from 1.74 to 1.49 mm. Diatomite applications significantly increased aggregate stability of all the experimental soils in all aggregate size fractions. In overall, aggregate stability increased from 28.04% to 45.70% with the application rate of 30%. Diatomite application also significantly increased soil moisture content at field capacity in SL textured soil. 30% diatomite increased field capacity in sand-textured soil in the percent of 43.78 as compared with control. Therefore it is suggested that diatomite may be considered as a soil amendment agent for improving soil physical characteristics. However, its effectiveness in enhancing soil properties depends on initial soil factors and texture. Moreover, since its protective effect against large aggregate (> 6.4 mm) formation and reducing effect on soil penetration resistance in clay textured soils, diatomite might be an alternative soil amendment agent in soil tillage practices and seedling.

A comparison of methods for estimating fractional vegetation cover in arid regions

We compared a set of methods for estimating the fractional vegetation cover (fc) of sparse desert vegetation over an arid region of southern Xinjiang, China. Six kinds of remote sensing inversion models (an NDVI regression, a spectral mixture analysis (SMA), a pixel dichotomy model, a three-band maximal gradient difference (TGDVI) model and two modified TGDVI models) were used to derive fc from remote sensing data, and the results were compared with fc values measured in the field to select an appropriate model to derive the fractional cover of sparse desert vegetation in arid regions. The NDVI regression based on field fc and the NDVI for the sampled pixels in September 2006 showed the highest precision, while the results of 2007 showed that the NDVI regression method is inappropriate for depicting vegetation characteristics in other growing season because the empirical model highly depend on the specified in situ measurement. The SMA approaches yielded higher precision than the other models, indicating that it is applicable for analysing the coverage of sparse desert vegetation. The pixel dichotomy model can yield a high precision based on finely detailed vegetation maps. However, it requires the measurement of many parameters. The TGDVI model is simple and easy to implement, and the values that it predicted for the coverage of high-density vegetation and barren areas were close to those measured in the field, but the fc values of sparsely vegetated areas were underestimated. The predictions of the modified TGDVI models were close to the values measured in the field, indicating that these modified models can reliably and effectively extract information on the fractional cover of sparse vegetation in an arid region. We analyzed the models’ sensitivity with respect to rainfall because the short-wavelength infrared bands used in the two TGDVI models proposed in this study are sensitive to moisture. The results showed that the modified TGDVI models’ accuracy was not affected by increasing soil moisture content caused by rain. However, the NDVI regression, SMA and TGDVI were sensitive to the change of soil moisture content. Moreover, the two modified TGDVI models yielded negative values for water sources, such as reservoirs and rivers, implying that they are effective for characterising water bodies. However, the modified TGDVI models cannot predict fc in snow- and glacier-covered regions, producing abnormally high rather than zero values. Additionally, the predictions before and after snowfall on the top of a mountain show a linear increasing relationship, suggesting that the short-wavelength infrared band may be useful to predict snow depth.

Plant water status and hydraulic conductance during flowering in the southern California coastal sage shrub Salvia mellifera (Lamiaceae)

Plant water status during flowering is important for plant reproduction, but the physiology of floral water use is not well understood. We investigated plant water status in relation to leaf and floral physiology in naturally occurring individuals of a semiarid shrub, Salvia mellifera E. Greene. We measured stomatal (g(s)) and corolla (g(c)) conductance to water vapor, transpiration from leaves (E(leaf)) and corollas (E(corolla)), leaf-specific hydraulic conductance (K(H)), bulk shoot water potential (Ψ(shoot)), and shoot water content on irrigated and control plants to analyze whether water was limiting to leaf and floral water use. Experimental irrigation caused a 203% increase in soil moisture content, a 20% increase in predawn Ψ(shoot), a 29% increase in midday Ψ(shoot), and a 92% increase in K(H). Floral and leaf gas exchange did not respond significantly to water addition, indicating that rates were at seasonal maxima and not limited by water availability. Total daily water use by corollas was ∼20% of total shoot water use. There were no significant differences in total daily shoot water use with water addition. Mean shoot water content (5.07 g) was close to mean daily shoot water use (6.71 g), indicating that the equivalent of total shoot water content turned over every 0.76 d. These results demonstrate that although irrigation improved whole-plant hydraulic conductance, gas exchange was not limited by water availability. Additionally, the high water use of flowers in this species might limit future flowering and reproductive success during dry years.

Soil organic carbon of degraded wetlands treated with freshwater in the Yellow River Delta, China

Supplying freshwater is one of the important methods to help restore degraded wetlands. Changes in soil properties and plant community biomass were evaluated by comparing sites with freshwater treatment versus reference sites following freshwater addition to wetlands of the Yellow River Delta for 7 years. The results indicated that soil organic carbon (SOC) was significantly increased in all wetland sites that were treated with freshwater compared to the reference sites. The treatment wetlands had greater total nitrogen (TN), lower pH and electrical conductivity and higher water content in the soil compared to the reference wetlands. In general, the upper soil layer (0–20 cm) had greater SOC than the lower soil layer (20–40 cm). The increase of SOC in the freshwater reintroduction wetlands was higher in the Suaeda salsa plant community (mean ± standard error) (6.89 ± 0.63 g/kg) and Phragmites communis plant community (4.11 ± 0.12 g/kg) than in the Tamarix chinensis plant community (1.40 ± 0.31 g/kg) in the upper soil layer. The differences were especially marked between the treated and reference wetlands for SOC and TN in the P. communis plant communities. The C:N ratio of the soil was significantly greater in the treated compared to the reference wetlands for the S. salsa plant community. Although the C: N ratios increased after treatment, they were all <25 suggesting that N availability was not limiting soil organic matter decomposition. Our results indicate that freshwater addition and the concomitant increase in soil moisture content enhances the accumulation of SOC in the Yellow River Delta.

Effects of Soil Moisture Content on the Residual Strength of Two Plants Root-Soil Composites

To study the effects of soil moisture content on the residual strength of root-soil composites and pure soil, the shear displacements of shear apparatus extend to 14mm. The results indicate that the residual strength of root-soil composites of two plants and pure soil increase at the beginning and then decrease, with increases of soil moisture content. When the residual strength reaches the maximum, the soil moisture content was about 10.77%.The residual strength of root-soil composites of Caragana microphylla Lam. and Artemisia sphaerocephala Krasch. are both higher than pure soil under four kinds of soil moisture content, the variation tendency of cohesive strength of two plants and pure soil are similar with residual strength. The internal fiction angle decreases when soil moisture content increases.

마이크로파를 적용한 에너지 효율적인 오염토양 정화를 위한 예비연구

A preliminary study for energy efficient soil heating and contaminant removal using microwave was conducted. Soils sampled from floodplain were heated with microwave oven, and soil heating property and energy efficiency were compared to those heated with electrical furnace. In addition the effects of water, soil organic matter, and contaminated diesel on soil heating with microwave were investigated. Even though the electrical power consumption of electrical furnace and microwave oven were similar, temperature of soil heated with microwave oven was significantly higher than that of soil heated with electrical furnace. The increase of soil moisture content delays the raise of soil temperature during heating it with microwave oven. However, the effects of total petroleum hydrocarbon (TPH) (<10%) in contaminated soil matrix and small amount of soil organic matter (<5%) on the increase of soil temperature by microwave were not significant. Further studies for contaminated soils with different texture using pilot scale microwave reactor are required for application of this technique in the field.

A laboratory experimental study of high-temperature thermal storage in the unsaturated soil using a vertical borehole heat exchanger

High-temperature thermal storage (HTTS) in soils is a promising energy-saving technology for space heating of buildings. Based on a laboratory experimental setup using a vertical borehole heat exchanger (BHE), dynamic changes of the soil temperature and moisture content during the thermal storage process are studied. Effects of the heat injection temperature and initial moisture content on the thermal performance of the BHE are analyzed. The results show that at the first thermal storage stage, the soil temperature and moisture content near the heat source may appear a temporary peak. Its occurrence depends on the initial soil moisture content, the heat injection temperature and the distance from the heat source. As the heat injection temperature increases, the heat transfer rate of the BHE increases greatly. As the initial soil moisture content increases, the temperature profile near the BHE tends to be deviated from the results predicted by heat conduction, thereby influencing the thermal performance of the BHE. The present results can provide useful guidelines for the design of an HTTS system. Copyright , Oxford University Press.

Applying a SPA model to examine the impact of climate change on GPP of open woodlands and the potential for woody thickening

AbstractWoody thickening is a global phenomenon that influences landscape C density, regional ecohydrology and biogeochemical cycling. The aim of the work described here is to test the hypothesis that increased atmospheric CO2 concentration, with or without photosynthetic acclimation, can increase gross primary production (GPP) and that this can explain woody thickening. We examine mechanisms underlying the response of GPP and highlight the importance of changes in soil water content by applying a detailed soil–plant–atmosphere model. Through this model, we show that CO2 enrichment with decreased or increased D and photosynthetic acclimation results in decreased canopy water use because of reduced gs. The decline in water use coupled with increased photosynthesis resulted in increased GPP, water‐use efficiency and soil moisture content. This study shows that this is a valid mechanism for GPP increase because of CO2 enrichment coupled with either a decrease or an increase in D, in water‐limited environments. We also show that a large increase in leaf area index could be sustained in the future as a result of the increased soil moisture content arising from CO2 enrichment and this increase was larger if D decreases rather than increases in the future. Large‐scale predictions arising from this simple conceptual model are discussed and found to be supported in the literature. We conclude that woody thickening in Australia and probably globally can be explained by the changes in landscape GPP and soil moisture balance arising principally from the increased atmospheric CO2 concentration. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Simulation Study of Atrazine-contaminated Soil Biodegradation by Strain W16

Abstract This paper studies the biodegradation of the atrazine-contaminated soil by the strain W16 (Rhodobacter sphaeroides sp.) under simulation conditions and analyzes the impacting factors of repairing process of atrazine-contaminated soil. The results show adding strain W16 can promote the degradation of atrazine in soil. W16s atrazine-degrading and W16 inoculation amount show positively correlated. When the inoculation amount of W16 was reduced to 1.2×105 cfu·g−1 soil, the strain W16s degradation ability of atrazine obviously weakened. The optimum temperature for strain W16 degradation atrazine in soil was 30°C and W16s atrazine-degrading rate on the 15th day was 96.86%. W16s atrazine-degrading rate in soil improved with the soil moisture content increase .When the soil moisture was 10%, the strain W16s atrazine-degrading ability was inhibited .While soil moisture content was more than 20%, atrazinedegrading rate was higher than 74.09% on the 15th day.

WHEAT YIELD AND ANTIOXIDANT ENZYMES RELATIONSHIP UNDER DIFFERENT SOIL WATER CONTENT

The objectives of this study were to examine the relationship between wheat yield cultivars (Sakha 93 and Giza 168) and antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and phenylalanine ammonia-lyase (PAL) activities under different soil water content i.e. low, moderate and high content by irrigation at 80% ETo (1280m³/fed.), by 100% ETo (1600m³/fed.) and120% ETo (1920m³/fed.), respectively. Two lysimeter experiments were carried out in two successive seasons i.e. 2006/2007 and 2007/2008 to estimate wheat yield and one experiment in plastic bags carried out of the greenhouse to determine the antioxidant enzymes of 28 days wheat plant under three different soil water content i.e. providing wheat seedlings with aforementioned treatment. Exposing wheat cultivars i.e. Giza 186 or Sakha 93 to water stress by irrigation at 80% ETo (1280 m³/fad.) exerted an increase in CAT, SOD, POD, APX and PAL over those irrigated at 100% ETo (1600 m³/fad.) or at 120% ETo (1920 m³/fad.), but the previous enzyme activities in the tissue of Saka 93 surpassed of that of Giza 168 cultivar. spike weight and weight of 100 grain/plant of Sakha 93 cultivar overcome that of Giza 168 at low soil moisture content (80% ETo), whereas opposite results were obtained at high and moderate water content (120% and 100% ETo) in the first growing season (2006/2007) and spike weight/plant in second growing season (2007/2008). There was a proportional relationship between increasing soil moisture content and grain yield/plant but the difference between moderate water content 100% ETo (1600 m³/fed.) and high water content 120% ETo (1920 m³/fed.) was not significant. Providing 28 days wheat plant with low water content, decreased wheat yield/plant and its attributes comparing with moderate water content for the two studied cultivars. The current study indicates that Sakha 93 cultivar was the most tolerant cultivar compared with Giza 168.

Comparison of Wind Erosion on Various Agricultural Lands

This investigation was conducted to compare wind erosion on three different agricultural lands (dryland, wastewater-irrigated land, and freshwater-irrigated land) in southeastern Iran. This region consists of 11500 km2 of arid to semi-arid lands and is one of the driest regions of the country with high population density. Average annual rainfall of the region ranges between 50 and 60 mm. The temperature data indicate that July is the warmest month, when the temperature rises to more than 50 °C, and January is the coldest month of the year, with a minimum temperature of −12 °C. The warm winds blow over the region of Sistan for about 120 days from June to September. The dominant wind directions are north and northwest. Twenty plots were designed randomly (in a completely randomized design) in this study to compare two irrigated areas, freshwater-irrigated land and wastewater-irrigated land, to dryland (control fields). The treatments were repeated three times. Ten data sets were taken during the experimental period, and the means were calculated and reported. The data indicated that wastewater-irrigated land benefitted from reduced soil erosion, increased soil fertility status (i.e., soil organic matter and nutrient contents), and increased soil moisture content. Soil losses by wind erosion in the wastewater-irrigated land, freshwater-irrigated area, and dryland in the study area were 185.2, 339.8, and 554.4 tons ha−1, respectively. In addition, the study sites lost 1.3, 2.4, and 4.6 cm of soil by wind erosion, respectively.

Variability of soil moisture and its relationship with surface albedo and soil thermal diffusivity at Astronomical Observatory, Thiruvananthapuram, south Kerala

Continuous observation data collected over the year 2008 at Astronomical Observatory, Thiruvananthapuram in south Kerala (76°59′E longitude and 8°30′N latitude) are used to study the diurnal, monthly and seasonal soil moisture variations. The effect of rainfall on diurnal and seasonal soil moisture is discussed. We have investigated relationships of soil moisture with surface albedo and soil thermal diffusivity. The diurnal variation of surface albedo appears as a U-shaped curve on sunny days. Surface albedo decreases with the increase of solar elevation angle, and it tends to be a constant when solar elevation angle is greater than 40°. So the daily average surface albedo was calculated using the data when solar elevation angle is greater than 40°. The results indicate that the mean daily surface albedo decreases with increases in soil moisture content, showing a typical exponential relation between the surface albedo and the soil moisture. Soil thermal diffusivity increases firstly and then decreases with the increase of soil moisture.

자귀풀 종자의 발아 및 출아에 미치는 환경요인

Several experiments were conducted in growth chambers and a greenhouse to determine the influence of various environmental factors on seed germination and seedling emergence of Indian jointvetch. Fully matured seeds of Indian jointvetch germinated only 42%. The germination percent increased as the storage temperature increased with time. More than 90% seeds germinated when the seeds were kept at 40℃ for seven months, but germination was 58.9 and 55.1% when kept at 25 and 4℃, respectively. Non-dormant seeds of Indian jointvetch germinated 91.1 and 92.4% at 30 and 30/25℃, respectively. Germination percent increased with increasing both prethermal temperature and time. The prethermal temperature of 90℃ for 40 minutes was the best for maximum germination (94.5%). Germination and growth of Indian jointvetch tended to decrease slightly until -0.3 MPa osmotic potential (water stress induction) and then declined drastically and the seeds did not germinate at below -0.5 MPa osmotic potential. Indian jointvetch seems to grow well in moist and flooding conditions since emergence and growth of seedling increased with increasing soil moisture content and the water level.

Role of final cover soil in regulating volatile organic compounds: emissions from solid waste disposal sites in developing countries

The objective of this study was to investigate the emission of Volatile Organic Compounds (VOCs) from solid waste disposal sites and their remediation at final cover soil. This research was conducted using field cover soil lysimeters placed at the surface of a solid waste dumping area and batch experiments in the laboratory. It was found that benzene, toluene, chloroform and perchloroethylene (PCE) were the major VOCs found in municipal solid wastes. Chloroform was found at highest concentration of 4240 ± 1215 nmol/m³ followed by benzene (831 ± 439 nmol/m³), PCE (478 ± 200 nmol/m³) and toluene (145 ± 93 nmol/m³). Batch experiments revealed that an increase in soil moisture content from 0% to 5% for clay and 0% to 10% for sandy loam reduced the adsorption of VOC on soil particles. Therefore, it is most important factor in controlling VOC emission from solid waste disposal site. The adsorption was increased with increasing VOC concentration in gaseous phase. By placing sandy loam and clay final cover soil layer, VOC emission from solid waste disposal site could be reduced by 60?99%.

The impact of environmental changes on the sediment loads of Norwegian rivers

Abstract The impact of unusual events on the sediment dynamics in rivers is discussed in this paper. The increase in the number of extreme precipitation events and other unusual weather events in Norway strongly suggests that weather conditions are changing. It is difficult to monitor sediment transport during large magnitude floods. It is however well known that they may deliver substantial amounts of sediment. The suspended sediment load in the upper Atna river during the springflood in 1995 was 44 times the mean load measured during the preceding years. The recurrence interval of this flood was estimated to be 100–200 years. The conditions during the occurrence of a particular flood event may also be of considerable importance and measurements during rainfall on frozen ground have indicated unusually high runoff and erosion rates. The seasonal distribution of runoff in several parts of Norway has changed in recent years and higher winter temperatures have produced an increase in the frequency of flood events. A very long lasting flood caused by a prolonged period of rain occurred in the Vikka stream during September to December 2000. The availability of sediment increased with the increasing soil moisture content in the area. As the ground became saturated, more active slope processes caused erosion rates to increase markedly. The combined effects of climate change and human impact on sediment transport in rivers appear to enhance downstream sediment delivery. Flood protection works along river channels prevent sediment from being deposited on the floodplain. River channels that have been lowered in order to reduce groundwater levels in agricultural floodplain areas will experience the same effect. During the last decade extensive ecological changes have taken place in the coastal areas of southern Norway as 90% of the sugar kelp forest has been lost. This change has been attributed to an apparent increase in sediment delivery to the sea along with a rise in sea temperatures.