This study aimed to link land cover/usechange to waterquality in an important water supply coastalcatchment. The approach followed a spatial and temporal analysis of historical catchmentlandusechange to assess how changes influenced waterquality and river flow in the Touws and Duiwe Rivers, southwestern Cape, South Africa. Each sub-catchment has unique characteristics which influence landuse and waterquality and the purpose was to analyse each one separately. Historical waterquality and flow analysis were based on the records available (Duiwe River: 1998–2013; Touws River: 1980–2013) together with rainfall data. Records were analysed to detect trends over time, which were linked to changes in landuse activities. Agriculture intensified rapidly in the Duiwe River catchment with most arable land cultivated by 1960 and water storage as farm dams escalating. Concentrations of nutrients and electrical conductivity were higher in the Duiwe River than in the more natural Touws River, and were positively correlated to river flows. Mean values for total nitrogen and electrical conductivity were 0.03 mg/L and 16.7 mg/L, respectively, in the Touws River and 0.25 mg/L and 127 mg/L, respectively, in the Duiwe River. Nutrient concentrations decreased in the Duiwe River after 2006 as fertilizer applications to pastures were reduced. The South African Target WaterQuality Ranges were exceeded at times and in the Touws catchment this appears to have been due to extensive fires. For instance, sodium concentrations reached a maximum of 1 874.5 mg/L in 1996 compared to a usual average concentration of 20.8 mg/L where the guidelines are between 0 and100 mg/L. The link between land cover/use and waterquality was demonstrated and when spatial heterogeneity of the catchments was altered by human or natural events, this was reflected in changes in the waterquality.
The runoff from a watershed indicates both the amount and intensity of precipitation, and the nature of the watershed in relation to the landuse/ cover and management aspects. Increasing pressure on land, and especially watercatchment zones, has a direct bearing on the quantity and quality of renewable water resources. Dense population coupled with increased agricultural activity upstream in the catchment’s settlement areas may lead to reduced flows in dry weather and low waterquality during rainy periods . This arises mainly from increased water demand for both agricultural and domestic use, which may reduce base flow during dry weather. Similarly, during the rainy season, increased runoff from densely populated and expansive agricultural areas is normally accompanied by increased sediment loads and other non-point source pollutants which lower waterquality. The situation is the same in Tumeiyo, one of the main sub basins of the Kimwarer River.
Despite the large number of plot to farm scale studies on technical mitigation options for waterquality, there is a relative paucity of evidence that these measures improve waterquality at larger spatial scales and also over long temporal scales. Evidence for the effects of mitigation measures on waterquality is required to account for public and private funds spent implementing those measures, to inform the scientific foundation for implementation of a measure and to help inform expectations about the potential in time and space for those measures to achieve anticipated waterquality targets. In some cases expectations of natural resource condition improvement are not realised despite expenditure on research, development, extension, incentives/subsidies and penalties, or insufficient monitoring exists to demonstrate whether change has occurred. Since 2002, a nationwide evaluation of over 50 years of conservation practices and 38 catchment assessment studies (the Conservation Effects Assessment Project) was initiated in the USA to account for USD 6 billion in expenditure on these practices (Weltz et al., 2005). In Australia, AUD 1.4 billion (USD 1.25 billion) was spent over 7 years to remediate salinity of soils and groundwater; however, there was little evidence of mitigation as a result of this expenditure (Pannell and Roberts, 2010). In the European Union, monitoring the impact that policies affecting agricultural practice have on waterquality is mandatory in zones declared as Nitrate Vulnerable Zones (e.g. in the England, France, Sweden, Czech Republic and the Walloon region of Belgium) and is a pre-requisite for stocking rates above a European Union cap on manure-nitrogen loading to be permitted. Some member states have identified the whole country as a Nitrate Vulnerable Zone (e.g. the Republic of Ireland, Austria, Luxembourg, Germany, Denmark) and have accordingly established national and agriculture-specific waterquality monitoring programs to compliment country-specific national regulations that include many of the measures highlighted in section 4 (Fraters et al., 2011).
Abstract. Quantifying the isolated and integrated impacts of landuse (LU) and climate change on streamflow is chal- lenging as well as crucial to optimally manage water re- sources in river basins. This paper presents a simple hydro- logic modeling-based approach to segregate the impacts of landuse and climate change on the streamflow of a river basin. The upper Ganga basin (UGB) in India is selected as the case study to carry out the analysis. Streamflow in the river basin is modeled using a calibrated variable infiltration capacity (VIC) hydrologic model. The approach involves de- velopment of three scenarios to understand the influence of landuse and climate on streamflow. The first scenario as- sesses the sensitivity of streamflow to landuse changes un- der invariant climate. The second scenario determines the change in streamflow due to change in climate assuming con- stant landuse. The third scenario estimates the combined ef- fect of changing landuse and climate over the streamflow of the basin. Based on the results obtained from the three scenarios, quantification of isolated impacts of landuse and climate change on streamflow is addressed. Future projec- tions of climate are obtained from dynamically downscaled simulations of six general circulation models (GCMs) avail- able from the Coordinated Regional Downscaling Experi- ment (CORDEX) project. Uncertainties associated with the GCMs and emission scenarios are quantified in the analysis. Results for the case study indicate that streamflow is highly sensitive to change in urban areas and moderately sensitive to change in cropland areas. However, variations in stream- flow generally reproduce the variations in precipitation. The combined effect of landuse and climate on streamflow is ob- served to be more pronounced compared to their individual impacts in the basin. It is observed from the isolated effects of landuse and climate change that climate has a more dom-
5.4.2 Hydrologic Impacts at Subbasin Scale: Comparison to Historical Baseline 184.108.40.206 Stream/Channel Flow
Flows out (discharge) of each subbasin via the main channel for the 9 scenarios were compared to values from the HB (Figure V-12). Average annual stream/channel flows ranged from 21.86 thousand acre-feet for subbasins along the western and southern edge of the LARB, to 198.98 thousand acre-feet at the basin outlet for the HB (Figure V-12j). For LP scenarios (S1, S2, and S3), all subbasin values for stream/channel flow fall below those form the HB; with little or no effect to stream/channel flow as a result of increased development (Figures V-12a, V-12b, and V-12c). With regard to the MP scenarios (S4, S5, and S6), 17 subbasins in the western and southwestern portions of the LARB exhibit values that are greater than those from the HB (Figures V-12d, V-12e, and V-12f). In terms of the effect of increased development, only S6 (Figure V-12f) portrays the impact of an increased amount of developed land. This is because only one subbasin (subbasin 19) in the Sinton area exhibits an increase in stream/channel
Studies have analyzed the effects of LULC change on hydrological fluxes in watersheds (e.g. -). Most of these studies analyze the effect of LULC change on the water balance without considering that a change in LULC may also induce a change in soil erosion sources and quantities. Recently, many studies have been launched to predict the hydrologic response of varying scenarios of landuse modification through the applica- tion of multiple models  . These research efforts have proven useful for planners and policy makers as a form of decision support for evaluating urbanized watersheds. This study examined future landuse scenarios in the FRW relative to their impact on surface-waterquality, e.g. discharge and sediment yield, using the hydro- logic model Soil and Water Assessment Tool (SWAT) . The future landuse scenarios: smart growth, plan trend and sprawl growth; produced for the study area were created using the Prescott Spatial Growth Model (PSGM) which is an extension in ArcGIS 9.3. The objective of the research was to identify sensitive areas that may be affected by increases in sediment yield from landusechange, such as conversion of agricultural land to urbanization by using an integrated approach.
In this study the majority of the literature was derived from North American and European studies although there are significant climatic and environmental differences. But these studies do provide ideas how the river waterquality can deteriorate and why. In addition there were few published studies available for Australian conditions related to the landuse affects on waterquality at a catchment scale or on a riparian zone basis. For example studies conducted in Rous River catchment in northern NSW Australia showed that elevated levels of nutrients were associated with leaching of excess fertiliser that have been applied in cane land (Eyre & Pepperell 1999). Ierodiacanou et al. (2005) studied a regional scale assessment of landusechange on nutrient exports by using an export coefficient model, remote sensing and GIS technique in south west Victoria. During period of 1980 to 2002 the modelled phosphorus and nitrogen loads were increased by 0.14 kg/ha and 1.37 kg/ha respectively when landuse changed from dryland pasture to more intensive agricultural activities such as cropping and irrigated pasture. Similarly, empirical studies have been done on the significant contribution of agricultural landuse (Nash et al. 2004; Webster et al. 2001) and managed pasture land (Nash & Halliwell 2000; Fleming & Cox 2001) to excessive phosphorus concentration in the waterways of South Australia. However, some review papers related to landuse and nutrient export in river systems have been written from an Australian prospective but these often use northern hemisphere data due to lack of relevant long-term Australian data sets (Young et al. 1996).
The objective of this research was to develop and test a framework that can be used to assess the effects of climate and land-usechange on the stream ecology in a basin. The current method of analyzing extreme events of streamflow is insufficient in non-stationary environments. Although tools and models are available for this assessment, no systematic approach is established. The proposed framework outlines and integrates the key steps and necessary procedures to assess the changes in streamflows. Precipitation and temperature data from four General Circulation Models (GCMs) and land cover data from a land-use model were coupled with a hydrologic model to simulate daily flows. The GCM monthly precipitation and temperature data were preprocessed using a downscaling method to achieve data on a refined spatial scale and a k-Nearest Neighbor algorithm was used to temporally disaggregate the data to a daily scale. The housing density data from the EPA Integrated Climate and Land-use Scenarios (ICLUS HD) were reclassified to be compatible with the USGS National Land Cover Database. The Soil and Water Assessment Tool (SWAT) was used to process the land-use and climate data in the basin. The flow values were used to estimate several Indicators of Hydrologic Alteration (IHA) which were then assessed for the amount of changes using the Range of Variability Approach (RVA). The hydrologic
Quantifying the hydrologic response of landuse/land cover change (LULCC) is of paramount im- portance to improve land management. This study was carried out to analyze the effect of LULCC on waterquality and quantity. LULCC of the watershed in 1986, 1999 and 2011 was analyzed from Landsat satellite images using supervised classification. Time series and point data were collected from the upper and lower sections of Wedesa, Wesha and Hallo Rivers. Waterquality parameters (turbidity, suspended solid (SS), total dissolved solid (TDS), pH, electric conductivity (EC), total organic carbon (TOC), ammonia, nitrate and phosphate) were analyzed in the laboratory. A consi- derable decline in forest and an increase in woodland were observed in the watershed during the indicated periods. Turbidity, SS, TDS and EC were significantly higher (P < 0.05) in the lower sec- tion of the rivers compared to the upper ones. Ammonia, nitrate and phosphate were higher in the lower section of some rivers compared to the upper ones. In general, waterquality in the upper watershed of the three rivers was better than the lower one with respect to considered parame- ters, which might be related to the observed LULCC. Most waterquality parameters varied (P < 0.05) seasonally in both the upper and lower sections of the rivers. Despite the irregular rainfall pattern and increased water consumption from the catchment, the annual discharge of the Ti- kur-Wuha River to Lake Hawassa shows an increasing trend. We concluded that the discharge is not only related to the upstream LULCC but also to the management of the Cheleleka wetland. However, further investigation is required to determine the dominant factors affecting inflow discharge to Lake Hawassa.
The simulation results in this study shows that significant changes in the stream flow in the Nyangores River have occurred. The simulated stream flow hydrographs shows a higher flow peaks for the 2010 land-use cover datasets than the 1995 land-use cover datasets. The monthly stream flow reveal that the discharge at the river gauging station have increased during the study period. The shift in peak flows between the study periods indicates the potential effects of LULC on the stream flow in the Nyangores River. The high peak flow in 2010 datasets indicates that for every rainfall event in the sub-catchment, rain water flows faster as surface runoff from the catchment to the stream. Such scenarios indicate that water interception in the sub-catchment is low and therefore less time for infiltration. This is caused by a decrease in Forest cover, decrease in Tree plantation and increase in Farmlands therefore reducing rain water interceptions leading to increase in surface run offs in the sub-catchment (Olang’, 2009)
Landuse and land cover changes are very common in developing countries whose economies are mainly dependent on agriculture and with rapid human population growth . Vegetation removal to prepare land for agriculture leaves soil susceptible to massive increase in soil erosion by wind and water. This reduces the fertility of the soil rendering it unsuitable for agricultural purposes, as well as transport large volumes of nitrogen, phosphorus, and sediments to streams which can lead to various negative impacts such as increased sedimentation, turbidity, eutrophication and coastal hypoxia of wetlands and rivers. The use of agrochemicals such as herbicides, pesticides, and in- organic fertilizers in modern-day agriculture has hugely contributed to increased levels of pollution in surface water bodies as well as contamination of groundwater through runoff and by way of leaching. This pollution in most cases is toxic to aquatic life  and humans. These impacts not only affect the immediate area but their effects can ex- tend to distant regions .
Within the context of proper management im- plementation or remedy arrangements adoption in a catchment a question arises – do we know how the water nitrate concentration can change in real units (milligrams, percentages) due to a modification of the catchmentlanduse or, rather, arable (ploughed) land proportion? During the two last decades, great progress has been achieved in the area of the development of the systems simu- lating hydrological processes and hydrochemical responses of a catchment. However, not unfrequent seems to be the trouble with a serious lack of the required data sets, especially in the sphere of basin management practice. This study attempts to ex- plore the relationships between N concentrations (expressed as C90 NO 3 – value in accordance with
III. The approach has shown that catchment specific data is appropriate in under- standing the dynamics of pollution behaviour in agreement with what NOAA Coastal Services Center (2004); Line et al. (2002); Oki (2003); and City and County of Honolulu (2007) have found out in similar studies. The summary of outcomes from the study undertaken include; 1) the development of a waterquality profile for Kuils-Eerste River catchment for an overall evaluation of the catchment and the different land-covers that contribute to the pollutant loading; 2) the identification of the various sources of contamination to allow for the implementation of appropriate management strategies; 3) the identifi- cation of sources of pollution which cause and sustain poor waterquality in the catchment; and 4) the development of a critical nonpoint monitoring pro- gramme for the Cape Town Metropolitan Authorities for the monitoring, management and mitigation of pollutant inputs in the catchment. The Event Mean Concentration (EMC) was derived as the flow-weighted mean concen- tration of contaminant. Individual storm EMC values were then summarised as either the arithmetic mean, the flow-weighted mean (total load from storm events divided by total discharge volume), or the median of event EMCs. Since the assessment of urban overland flow quality of Kuils-Eerste river catchment required a consideration of different types of land-cover, it was rep- resented by the event mean concentration (EMC) value. The EMC determined, represent the concentration of a specific pollutant contained coming from a particular land-cover type within the catchment. The aim of the study was ful- filled which sought to explain how the quality of surface runoff varied on dif-
Hydrologic Response Units (HRUs) in SWAT (Gassman et al., 2007), and the same term
is also used here. Each HRU is assumed to be homogeneous, and is characterized by
representative values of CN (CN i ) and I a (I ai ). During a rainfall event, the HRU with the smallest of the I ai s will be the first to generate runoff. Assuming that this runoff reaches the watershed outlet, by definition, the I a of the watershed should be equal to the smallest of the I ai s. This could even be zero if the watershed has surfaces such as open water bodies that cannot abstract the rainfall.
drainage basin located in the west central part of the Lower Peninsula of Michigan, USA (Figure 1). Important species like the walleye (Sander vitreus), steelhead (Oncorhynchus
mykiss), and chinook salmon (Oncorhynchus tshawytscha) use this watershed as
spawning and nursery habitat. This watershed was chosen in part for proximity and also the wealth of existing data on macroinvertebrates and waterquality (Ray et al., 2010; Wiley et al., 2010). Specific 2 nd to 3 rd order cold-water trout tributary streams were selected within the Muskegon River watershed with help from the Michigan Department of Natural Resources (Rich O’Neal, personal communication). The Muskegon river watershed is generally dominated by forest, agriculture, and urban areas (O’Neal, 1997; Ray et al., 2010) and my streams were located in sections with mostly forest, wetlands, and agriculture. Study streams were placed along a gradient (low to high) of % agriculture in a 100 m buffer on both sides of stream and are as follows: Lower Cedar, Mosquito, Upper Cedar, Bigelow, Handy, and Brooks Creek.
The Wurzburg University’s REMO model was used for forecasts of climate change. This climatic model is based on the ECHAM 5 model developed at the Max Plank Institute (Germany). That is the model of global at- mosphere circulation. It is used for calculation of global and regional models of climate change. The A1B sce- nario of average warming as a result of greenhouse gas emission was played in the model. Given model allowed constructing the artificial temperature and rainfall series until 2100. The modeling results were calibrated. The calibration consisted in finding of coefficients that linked the modeled climatic data (REMO) to real observa- tions. The coefficients were determined for a period of time, for which the observation data were available. The calibration was made against the calculated values of evapotranspiration and separately against temperature and rainfall.
Between 2006 and 2012, conversion of 485,000 acres of grassland to cropland in eastern South Dakota was reported. In 2012, the Big Sioux River (BSR) running through most of eastern South Dakota was listed among the dirtiest rivers in the nation. This rating convinced state authorities to study trends of land cover changes in the BSR watershed and its association with BSR waterquality with respect to increases in nitrate levels. This research i) quantifies spatial and temporal changes in the land cover types within the BSR watershed, and ii) identifies any correlation between these changes and changes in BSR nitrate levels. It uses the Cropland Data Layer (CDL) to characterize and determine rates of Land Cover Changes (LCC), and the non-parametric Mann-Kendall test to identify statistically significant increasing and decreasing LCC trends within the BSR watershed. Similarly, nitrate data collected from 11 gauging stations operating in the BSR watershed were analyzed using the Mann-Kendall test to identify any trends. For all the land cover classes and gauging stations that were identified as statistically significant, a Sen’s Slope estimate was used to estimate their magnitudes. Only
The rate of expansion of cultivated land before 1995 was higher than after 1995. Conversely, the area of the forest land decreased in 1985 and 1995 with reference to the 1973 base- line. However, after 1995, the forest’s size increased again, whereas cultivated land decreased. The increased forest cov- erage and the decrease in cultivated land over the period 1995 to 2010 showed that the environment was recovering from the devastating drought, and forest clearing for firewood and cultivation due to population growth has been minimised. This could be due to the afforestation programme, which the Ethiopian government initiated, and to the extensive soil- and-water conservation measures carried out by the commu- nity. Since 1995, eucalyptus tree plantations expanded sig- nificantly across the country at the homestead level for fire- wood, construction materials, charcoal production, and in- come generation (Woldesenbet et al., 2017b). In summary, forest coverage decreased by 1.8 %, while both bushes and shrubs as well as cultivated land increased by 0.8 % and 1 %, respectively, from the original 1973 level to the 2010 period. This result agrees well with other studies (Gebremicael et al., 2013; Rientjes et al., 2011; Teferi et al., 2013; Woldesenbet et al., 2017b), which reported a significant conversion of nat- ural vegetation cover into agricultural land.
Abstract}Secondary databases, GIS and multivariate analysis tools were used to determine whether there was a correlation between waterquality and landscape characteristics within three local southern Ontario watersheds. Whole catchment and 100 m buﬀer zone inﬂuences on waterquality over three seasons were compared. Chemical ﬂuxes were also calculated and used to compare the loading of pollutants to downstream environments. Urban landuse had the greatest inﬂuence on waterquality. The inﬂuence of agricultural landuse was variable and did not agree with the results of other studies. The only natural landscape variables that appeared to have an inﬂuence on waterquality were slope and silt–clay surﬁcial geology deposit. There was a clear trend of increased chemical ﬂuxes with increasing urban landuse intensity within a watershed. Forested landuse appeared important in mitigating waterquality degradation. The catchment landscape characteristics appeared to have slightly greater inﬂuence on waterquality than the 100 m buﬀer. The results of this study may have been inﬂuenced by the scale and accuracy of databases used. The secondary data were useful in determining major trends in waterquality and possible non-point origins of surface water pollution, and in identifying areas that are in need of further investigation. # 2001 Elsevier Science Ltd. All rights reserved
Taiwan is a mountainous island, where the mountains, hills and the plateaus account for about 70% of its total area, thus, most of the cities are located in the coastal plains and basins. Typhoons and storms occur frequently every year, therefore, almost every town and city and all kinds of productive activities are affected constantly by the flood relevant natural hazards (Kung et.al, 2009), especially in land subsidence areas.