Hybrid moving block bootstrap for stochastic simulation of multi-site multi-season streamflows

The Hybrid approach introduced by the authors for at-site modeling of annual and periodic streamflows in earlier works is extended to simulate multi-site multi-season streamflows. It bears significance in integrated river basin planning studies. This hybrid model involves: (i) partial pre-whitening of standardized multi-season streamflows at each site using a parsimonious linear periodic model; (ii) contemporaneous resampling of the resulting residuals with an appropriate block size, using moving block bootstrap (non-parametric, NP) technique; and (iii) post-blackening the bootstrapped innovation series at each site, by adding the corresponding parametric model component for the site, to obtain generated streamflows at each of the sites. It gains significantly by effectively utilizing the merits of both parametric and NP models. It is able to reproduce various statistics, including the dependence relationships at both spatial and temporal levels without using any normalizing transformations and/or adjustment procedures. The potential of the hybrid model in reproducing a wide variety of statistics including the run characteristics, is demonstrated through an application for multi-site streamflow generation in the Upper Cauvery river basin, Southern India. (C) 2004 Elsevier B.V. All rights reserved.

Mahanadi streamflow: climate change impact assessment and adaptive strategies

Impacts of climate change on hydrology are assessed by downscaling large scale general circulation model (GCM) outputs of climate variables to local scale hydrologic variables. This modelling approach is characterized by uncertainties resulting from the use of different models, different scenarios, etc. Modelling uncertainty in climate change impact assessment includes assigning weights to GCMs and scenarios, based on their performances, and providing weighted mean projection for the future. This projection is further used for water resources planning and adaptation to combat the adverse impacts of climate change. The present article summarizes the recent published work of the authors on uncertainty modelling and development of adaptation strategies to climate change for the Mahanadi river in India.

Detection of moisture stress by indicator plots — A simulation

The possibility of advanced indication of moisture stress in a crop by small prepared plots with compacted or partially sand-substituted soils is examined by an analytical simulation. A series of soils and three crops are considered for the simulation. The moisture characteristics of the soils are calculated with an available model. Using average potential evapotranspiration values and a simple actual evapotranspiration model, the onset of moisture stress in the natural and indicator plots is calculated for different degrees of sand substitution and compaction. Cases where sand substitution fails are determined. The effect of intervening rainfall and limited root depth on the beginning of moisture stress is investigated.

Development of a low-cost portable colorimeter for the estimation of fluoride in drinking water

People in many countries are affected by fluorosis owing to the high levels of fluoride in drinking water. An inexpensive method for estimating the concentration of the fluoride ion in drinking water would be helpful in identifying safe sources of water and also in monitoring the performance of defluoridation techniques. For this purpose, a simple, inexpensive, and portable colorimeter has been developed in the present work. It is used in conjunction with the SPADNS method, which shows a color change in the visible region on addition of water containing fluoride to a reagent solution. Groundwater samples were collected from different parts of the state of Karnataka, India and analysed for fluoride. The results obtained using the colorimeter and the double beam spectrophotometer agreed fairly well. The costs of the colorimeter and of the chemicals required per test were about Rs. 250 (US$ 5) and Rs. 2.5 (US$ 0.05), respectively. In addition, the cost of the chemicals required for constructing the calibration curve was about Rs. 15 (US$ 0.3). (C) 2010 Elsevier B.V. All rights reserved.

Ecology of the swampy relic forests of Kathalekan from central Western Ghats, India

Introduction of agriculture three millennia ago in Peninsular India’s Western Ghats altered substantially ancient tropical forests. Early agricultural communities, nevertheless, strived to attain symbiotic harmony with nature as evident from prevalence of numerous sacred groves, patches of primeval forests sheltering biodiversity and hydrology. Groves enhanced heterogeneity of landscapes involving elements of successional forests and savannas favouring rich wildlife. A 2.25 km2 area of relic forest was studied at Kathalekan in Central Western Ghats. Interspersed with streams studded with Myristica swamps and blended sparingly with shifting cultivation fallows, Kathalekan is a prominent northernmost relic of southern Western Ghat vegetation. Trees like Syzygium travancoricum (Critically Endangered), Myristica magnifica (Endangered) and Gymnacranthera canarica (Vulnerable) and recently reported Semecarpus kathalekanensis, are exclusive to stream/swamp forest (SSF). SSF and non-stream/swamp forest (NSSF) were studied using 18 transects covering 3.6 ha. Dipterocarpaceae, its members seldom transgressing tropical rain forests, dominate SSF (21% of trees) and NSSF (27%). The ancient Myristicaceae ranks high in tree population (19% in SSF and 8% in NSSF). Shannon-Weiner diversity for trees is higher (>3) in six NSSF transects compared to SSF (<3). Higher tree endemism (45%), total endemic tree population (71%) and significantly higher above ground biomass (349 t/ha) cum carbon sequestration potential (131 t/ha) characterizes SSF. Faunal richness is evident from amphibians (35 species - 26 endemics, 11 in IUCN Red List). This study emphasizes the need for bringing to light more of relic forests for their biodiversity, carbon sequestration and hydrology. The lives of marginal farmers and forest tribes can be uplifted through partnership in carbon credits, by involving them in mitigating global climatic change through conservation and restoration of high biomass watershed forests.

Modelling the chemical weathering fluxes at the watershed scale in the Tropics (Mule Hole, South India): Relative contribution of the smectite/kaolinite assemblage versus primary minerals

We investigate the chemical weathering processes and fluxes in a small experimental watershed (SEW) through a modelling approach. The study site is the Mule Hole SEW developed on a gneissic basement located in the climatic gradient of the Western Ghats, South India. The model couples a lumped hydrological model simulating the water budget at the watershed scale to the WITCH model estimating the dissolution/precipitation rates of minerals using laboratory kinetic laws. Forcing functions and parameters of the simulation are defined by the field data. The coupled model is calibrated with stream and groundwater compositions through the testing of a large range of smectite solubility and abundance in the soil horizons. We found that, despite the low abundance of smectite in the dominant soil type of the watershed (4 vol.%), their net dissolution provides 75% of the export of dissolved silica, while primary silicate mineral dissolution releases only 15% of this flux. Overall, smectites (modelled as montmorillonites) are not stable under the present day climatic conditions. Furthermore, the dissolution of trace carbonates in the saprolitic horizon provides 50% of the calcium export at the watershed scale. Modelling results show the contrasted behavior of the two main soil types of the watershed: red soils (88% of the surface) are provider of calcium, while black soils (smectite-rich and characterized by a lower drainage) consumes calcium through overall carbonate precipitation. Our model results stress the key role played by minor/accessory minerals and by the thermodynamic properties of smectite minerals, and by the drainage of the weathering profiles on the weathering budget of a tropical watershed. (C) 2010 Elsevier B.V. All rights reserved.

Response of fungal and actinobacterial communities to water-level drawdown in boreal peatland sites

"We used PCR-DGGE fingerprinting and direct sequencing to analyse the response of fungal and actinobacterial communities to changing hydrological conditions at 3 different sites in a boreal peatland complex in Finland. The experimental design involved a short-term (3 years; STD) and a long-term (43 years; LTD) water-level drawdown. Correspondence analyses of DGGE bands revealed differences in the communities between natural sites representing the nutrient-rich mesotrophic fen, the nutrient-poorer oligotrophic fen, and the nutrient-poor ombrotrophic bog. Still, most fungi and actinobacteria found in the pristine peatland seemed robust to the environmental variables. Both fungal and actinobacterial diversity was higher in the fens than in the bog. Fungal diversity increased significantly after STD whereas actinobacterial diversity did not respond to hydrology. Both fungal and actinobacterial communities became more similar between peatland types after LTD, which was not apparent after STD. Most sequences clustered equally between the two main fungal phyla Ascomycota and Basidiomycota. Sequencing revealed that basidiomycetes may respond more (either positively or negatively) to hydrological changes than ascomycetes. Overall, our results suggest that fungal responses to water-level drawdown depend on peatland type. Actinobacteria seem to be less sensitive to hydrological changes, although the response of some may similarly depend on peatland type. (C) 2009 Elsevier Ltd. All rights reserved."

Estimation of variables at ungaged locations by empirical orthogonal functions

A technique based on empirical orthogonal functions is used to estimate hydrologic time-series variables at ungaged locations. The technique is applied to estimate daily and monthly rainfall, temperature and runoff values. The accuracy of the method is tested by application to locations where data are available. The second-order characteristics of the estimated data are compared with those of the observed data. The results indicate that the method is quick and accurate.

Ilman epäpuhtauksien vaikutuksesta maaperään ja pohjaveteen Tampereen ja Kuusankosken ympäristössä

Engl. summary: On the influence of air pollution on soil and groundwater in the Tampere and Kuusankoski regions

Pikasuodatus pohjaveden raudan poistossa

Rapid filtration in iron removal from groundwater.

Yhdyskuntien vedenhankinnalle tärkeät pohjavesialueet

Groundwater areas important for public water supply.

Analysis of an Aquifer-water table aquitard system

The problem of pumping an aquifer in an aquifer-water table aquitard system is considered, accounting for the elastic properties of both the aquifer and the aquitard, the gravity drainage in the aquitard and treating the water table as an unknown boundary. The coupled partial differential equations are nondimensionalised, yielding three principal parameters governing the problem. The numerical solution of these equations is obtained for a wide range of parameter values. Type curves are generated and their use is illustrated through a field application.

Analysis of flow near a dug well in an unconfined aquifer

A numerical analysis of flow to a dug well in an unconfined aquifer is made, taking into account well storage, elastic storage release, gravity drainage, anisotropy, partial penetration, vertical flow and seepage surface at the well face, and treating the water table in the aquifer and water level in the well as unknown boundaries. The pumped discharge is maintained constant. The solution is obtained by a two-level iterative scheme. The effects of governing parameters on the drawdown, development of seepage surface and contribution from aquifer flow to the total discharge are discussed. The degree of anisotropy and partial penetration are found to be the parameters which affect the flow characteristics most significantly. The effect of anisotropy on the development of seepage surface is very pronounced.

Meridional propagation of large-scale monsoon convective zones

Observational studies indicate that the convective activity of the monsoon systems undergo intraseasonal variations with multi-week time scales. The zone of maximum monsoon convection exhibits substantial transient behavior with successive propagating from the North Indian Ocean to the heated continent. Over South Asia the zone achieves its maximum intensity. These propagations may extend over 3000 km in latitude and perhaps twice the distance in longitude and remain as coherent entities for periods greater than 2-3 weeks. Attempts to explain this phenomena using simple ocean-atmosphere models of the monsoon system had concluded that the interactive ground hydrology so modifies the total heating of the atmosphere that a steady state solution is not possible, thus promoting lateral propagation. That is, the ground hydrology forces the total heating of the atmosphere and the vertical velocity to be slightly out of phase, causing a migration of the convection towards the region of maximum heating. Whereas the lateral scale of the variations produced by the Webster (1983) model were essentially correct, they occurred at twice the frequency of the observed events and were formed near the coastal margin, rather than over the ocean. Webster's (1983) model used to pose the theories was deficient in a number of aspects. Particularly, both the ground moisture content and the thermal inertia of the model were severely underestimated. At the same time, the sea surface temperatures produced by the model between the equator and the model's land-sea boundary were far too cool. Both the atmosphere and the ocean model were modified to include a better hydrological cycle and ocean structure. The convective events produced by the modified model possessed the observed frequency and were generated well south of the coastline. The improved simulation of monsoon variability allowed the hydrological cycle feedback to be generalized. It was found that monsoon variability was constrained to lie within the bounds of a positive gradient of a convective intensity potential (I). The function depends primarily on the surface temperature, the availability of moisture and the stability of the lower atmosphere which varies very slowly on the time scale of months. The oscillations of the monsoon perturb the mean convective intensity potential causing local enhancements of the gradient. These perturbations are caused by the hydrological feedbacks, discussed above, or by the modification of the air-sea fluxes caused by variations of the low level wind during convective events. The final result is the slow northward propagation of convection within an even slower convective regime. The ECMWF analyses show very similar behavior of the convective intensity potential. Although it is considered premature to use the model to conduct simulations of the African monsoon system, the ECMWF analysis indicates similar behavior in the convective intensity potential suggesting, at least, that the same processes control the low frequency structure of the African monsoon. The implications of the hypotheses on numerical weather prediction of monsoon phenomenon are discussed.

Kaupunkipurot Helsingissä - Veden laatu vuonna 2004

In recent years urban hydrology and individual urban streams have been in focus and subjects to research also in Helsinki. However, until now there has been lack of research covering simultaneously the whole area of the city of Helsinki. The aim of this study was to find out the general state of water quality in small urban streams in the city of Helsinki. 21 streams were studied: Mätäjoki, Korppaanoja, Mätäpuro, Näsinoja-Tuomarinkylänoja, Tuomarinkartanonpuro, Kumpulanpuro, Tapaninkylänpuro, Tapaninvainionpuro, Puistolanpuro, Longinoja, Säynäslahdenpuro, Viikinoja, Porolahdenpuro, Mustapuro, Marjaniemenpuro, Mellunkylänpuro, Vuosaarenpuro, Rastilanpuro, Ramsinkannaksenpuro, Skatanpuro and Yliskylänpuro. Water samples were collected from 48 sampling points, each stream having at least one point. Four water samples were collected from each point, sampling periods being 9.-11.2., 26.-28.4., 29.6.-1.7. and 25.-27.10.2004. Field measurements associated with water sampling included water temperature, oxygen concentration, pH and electrical conductivity. Water samples were analysed in the Laboratory of Physical Geography in the University of Helsinki and in the Environmental Laboratory of the City of Helsinki Environment Centre for following properties: suspended solids, dissolved substances, alkalinity, principal anions and cations (Na+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, PO43- and SO42-), colour, turbidity, biological and chemical oxygen demand (BOD7 and CODMn-values), nutrient concentrations and bacterial indicators of hygienic quality. The main water quality issues found in this study were low oxygen levels in many streams and poor hygienic quality at least occasionally. E.g. in summer oxygen levels were under 60 % in every stream. Amount of total dissolved substances and nutrients were high in some of the streams studied. Compared to other Finnish streams the values of alkalinity and pH were higher. Although these problems were common, the variation between different streams and sampling points was significant. This was probably due to local conditions. Best overall water quality was found in Mätäpuro and Tuomarinkartanonpuro streams. Seasonal variation was evident in almost all water quality properties. For example the total amount of dissolved substances was largest in winter and decreased during the year. Colour and turbidity were smallest in winter and increased towards the end of the year. The same was true for suspended solids, which had smallest concentration in winter and greatest in autumn. It must be kept in mind that the spring samples were collected after the spring flood otherwise the largest suspended solid concentrations would have been expected in spring. Finnish general water quality classification was used to assess the quality of urban stream waters. Its suitability for small urban streams is not, however, completely trouble-free. This classification does not take into account the quick changes in such small streams but evaluates only the yearly mean values. This can oversimplify the picture of the water quality situation in the streams. Also in order to better reflect the urban environment the analysed water quality properties should also include total dissolved substances and e.g. concentrations of chloride and sodium.