Surface Water Supply Research Articles

Analytical Hierarchical Process (AHP) Techniques and Geospatial Technologies for Groundwater Potential Zone Mapping

Due to its consistent availability, acceptable natural quality, and ease of direct diversion to the underprivileged population, groundwater is a vital source of water supply. It can also be transported there more swiftly and inexpensively. Exploring groundwater potential zones (GWPZs) maps is therefore essential, especially in semi-arid environments with insufficient surface water supplies. The groundwater potential of the research area is assessed using geographic information system methods and remote sensing data. Operational Land Imager 8 data, digital elevation models, soil data, rainfall data, and dug-out-well data were utilized to estimate the characteristics that influence groundwater potential and recharge zones. Maps of lineament density, drainage density, rainfall distribution, topographic-wetness index, land use/land cover, land-surface temperature, slope and soil were produced. These were overlaid based on analytical hierarchical process weightage prioritization at a constituency ratio of 0.05. The resulting map was divided into very high, high, moderate, low and very low groundwater potential zones. The area dimensions of these categories are 116005.5 ha, 35822.4 ha, 20152 ha, 2459 ha and 259245 respectively. Accordingly, the north-east part of the study area is expected to have very high ground‐water potential. Out of the 55 operational wells sampled, 72.73 % were situated in areas with very high groundwater potential. The high category had 10.91% while the moderate, low and very low categories remained 7.27%, 5.45% and 3.64% respectively. The overall result indicates that the model approach is reliable and can be adopted for a reliable characterization of GWPZs in any semi-arid/ arid environment.

Mobility and Degradation of Pesticides in Soil-Risk to Groundwater Contamination

Pesticides are used in modern agriculture to prevent crop losses by different pests and allow sustentation of the current crop yields. The pesticides after their use enter the environment viz., soil, water and air, then undergo various interactions and complex transformations resulting in the formation of multiple metabolites. The fate of pesticides in the environment depends on the properties of pesticide, soil and some other miscellaneous factors. Pesticides and their metabolites may move downward and reach groundwater under the effect of gravity, percolation, agricultural runoff or backsiphoning, hence there is risk to groundwater contamination. Chemicals have been noticed in groundwater, drinking water and surface water supplies. Therefore, research on ill-effects of the pesticide use and their fate in the environment is of great concern. The indigenous micro-flora is successful in biodegradation and removal of xenobiotics. So, in order to ensure public safety as well as the environmental protection from the chemical use, the pesticide use must be judicious and biodegradation of such chemicals to reduce their residues in agricultural products needs to be escalated.

Pertinent Water-Saving Management Strategies for Sustainable Turfgrass in the Desert U.S. Southwest

Drought and heat stresses are major challenges for turfgrass management in the desert southwest of the United States where rainfall is insufficient to support managed turfgrass growth. Irrigation water availability and its quality are increasingly strained due to diminishing surface water supplies. Unprecedented drought conditions threaten the reliance on groundwater supplies that are heavily scrutinized for irrigation practices on landscape and recreational turfgrass. Therefore, development of drought tolerant cultivars, lower input turf management strategies that sustains turfgrass appearance and performance with less irrigation water, and tolerance to higher seasonal temperatures will be critically important. Sustainability of acceptable quality turfgrass can be accomplished through harnessing the natural genetic variation, genetic manipulation using modern genomic technology, and optimizing turfgrass management practices for improved drought tolerance. Besides persistent efforts of varietal development and improved turfgrass management for drought tolerance and performance, redefining the quality of irrigated turfgrass for consumers to align with the environmental conditions is envisioned to foster a sustainable golf, sports fields, and landscape turfgrass industry in the region. A comprehensive study encompassing different turfgrass species and enhancing management practices to achieve acceptable performing turfgrass as well as outreach education to improve public perception of realities for a “green” environment will be critically important. The recent developments in turfgrass science and contemporary communication platforms are instrumental in increasing awareness for a sustainable turfgrass paradigm and sustain eco-tourism of the region.

Water Security in South Asian Cities: A Review of Challenges and Opportunities

Achieving water security in South Asian cities will require a realistic and holistic understanding of the challenges that are growing in extent and severity. These challenges include the rapid rise in urban household water demand due to both overall population growth and increasing urbanization rate. Additionally, surface water supply in closed river basins is fully utilized, and there is little opportunity in these regions to increase the extraction of surface water to meet rising demands. Furthermore, groundwater extraction in most regions exceeds natural recharge rates, leading to rapidly falling annual water tables and seasonal depletion in hard rock regions and to gradually declining water tables requiring deeper wells and increased pumping effort in alluvial regions. Additionally, even in cities with abundant water resources, poorer segments of the population often face economic water scarcity and lack the means to access it. Nevertheless, there are important potential engineering opportunities for achieving water security in South Asian cities. Much withdrawn water is lost due to urban water distribution inefficiency, and a range of proven techniques exist to improve distribution. Metering of urban water can lead to structural improvements of management and billing, though the water needs of the poorest city residents must be ensured. Industrial water-use efficiency can be significantly improved in manufacturing and electricity generation. The quantities of wastewater generated in South Asia are large, thus treating and reusing this water for other purposes is a strong lever in enhancing local water security. There is limited potential for rooftop rainwater harvesting and storage, though capture-enhanced groundwater recharge can be important in some areas. Some individual inter-basin transfer projects may prove worthwhile, but very-large-scale projects are unlikely to contribute practically to urban water security. Overall, the water challenges facing South Asian cities are complex, and although no single intervention can definitively solve growing problems, numerous actions can be taken on many fronts to improve water security.

Reactivity of Nitrate with Zero-Valent Iron

Elevated nitrate concentrations in groundwater and surface water supplies can negatively impact the quality of the environment and human health. Recent studies have examined the use of zero-valent iron technology to treat nitrate-contaminated groundwater. Mechanistic aspects of nitrate reduction by zero-valent iron are unresolved. This project investigated the kinetics and mechanism of nitrate reduction by zero-valent iron under anoxic conditions and under oxic conditions. Stirred-batch reactions were studied over environmentally relevant ranges of reactant concentration, pH, and temperature. A complex rate expression was derived with a 1.8 order dependence on nitrate, a 1.4 order dependence on zero-valent iron, and a fractional order (0.8) dependence on proton concentrations under anoxic conditions. An apparent activation energy of 35 kJ mol−1 was observed indicating that nitrate reduction was diffusion controlled under our conditions. Furthermore, the calculated entropy of activation value of −162 J mol−1K−1 indicates that this reaction occurred by an associative mechanism. Under oxic conditions, there was a lag period in nitrate reduction where oxygen was preferentially utilized, leading to a slower rate of nitrate reduction when compared with anoxic conditions. These rate data can be used in predicting nitrate disappearance in nitrate-contaminated groundwater and wastewater treated with zero-valent iron.

Cost-effective management measures for coastal aquifers affected by saltwater intrusion and climate change.

Sustainable management of natural water resources and food security in the face of changing climate conditions is critical to the livelihood of coastal communities. Increasing inundation and saltwater intrusion (SWI) will likely adversely affect agricultural production and the associated beach access for tourism. This study uses an integrated surface-ground water model to introduce a new approach for retardation of SWI that consists of placing aquifer fill materials along the existing shoreline using Coastal Land Reclamation (CLR). The modeling results suggest that the artificial aquifer materials could be designed to decrease SWI by increasing the infiltration area of coastal precipitation, collecting runoffs from the catchment area, and applying treated wastewater or desalinated brackish water-using coastal wave energy to reduce water treatment costs. The SEAWAT model was applied to verify that it correctly addressed Henry's problem and then applied to the Biscayne aquifer, Florida, USA. In this study, to better inform Coastal Aquifer Management (CAM), we developed four modeling scenarios, namely, Physical Surface Barriers (PSB), including the artificial aquifer widths, permeability, and side slopes and recharge. In the base case scenario without artificial aquifer placement, results show that seawater levels would increase aquifer salinity and displace large amounts of presently available fresh groundwater. More specifically, for the Biscayne aquifer, approximately 0.50% of available fresh groundwater will be lost (that is, 41,192 m3) per km of the width of the aquifer considering the increasing seawater level. Furthermore, the results suggest that placing the PSB aquifer with a smaller permeability of <100 m per day at a width of approximately 615 m increases the available fresh groundwater by approximately 45.20 and 43.90% per km of shoreline, respectively. Similarly, decreasing the slope on the aquifer-ocean side and increasing the aquifer recharge will increase freshwater availability by about 43.90 and 44.50% per km of the aquifer. Finally, placing an aquifer fill along the shallow shoreline increases net revenues to the coastal community through increased agricultural production and possibly tourism that offset fill placement and water treatment costs. This study is useful for integrated management of coastal zones by delaying aquifer salinity, protecting fresh groundwater bodies, increasing agricultural lands, supporting surface water supplies by harvesting rainfall and flash flooding, and desalinating saline water using wave energy. Also, the feasibility of freshwater storage and costs for CAM is achieved in this study.

Analysis of Rural Areas of Ukraine on the Basis of ESA WorldCover 2020

At present, GIS technologies penetrate various spheres of socio-economic life of humankind. In this paper, based on GIS technologies, the main classes of the land cover of Ukraine were analysed with further in-depth study in terms of regions and rural and urban areas. The results of this study are based on ESA WorldCover data; according to them, 32% of Ukraine’s territory can be attributed to urban areas, while 68% – to rural areas. In general, the analysis showed that Ukraine is characterised by a high degree of land using, so the land that was cultivated in 2020 accounted for 55.5% of its area. 70% of rural areas comprise cultivated areas, 30% – in urban areas. The leaders among the oblasts with the largest share of cultivated lands are Zaporizhzhia (76%), Kirovohrad (76%), Mykolaiv (77). An inherent feature of Ukraine’s land structure is a considerable share of land (15.3%) under meadows, hayfields, and pastures, which are vital in restoration and preservation and as an essential element of regional ecosystems. 66% of the territories of this class are concentrated in rural areas, on urban areas – 34%. Most of them are in Luhansk (26%), Lviv (24%) and Volyn (22%) oblasts. The level of forest cover in Ukraine is 23.3%, with 17.7% being forests and the other 6% – protective forest belts, orchards, and arboretums. Rural areas account for 64% of forested areas. The most forested areas are Zakarpattia (68%), Ivano-Frankivsk (54%) and Zhytomyr (45%), while the least forested are Kherson (4%), Zaporizhzhia (5%) and Mykolaiv (6%). In general, 71% of forested areas are rural and 29% are urban. In Ukraine, the share of surface waters covering the geographical area is 2.4%, of which 71% is in rural territories and 29% – in urban territories. Cherkasy (5%), Zaporizhzhia (6%), and Kherson (8%) oblasts are the top three oblasts in terms of surface water supply with 64%, 63% and 82% in rural areas, respectively (Figure 8). In turn, the oblasts with the smallest share of open water areas are Zhytomyr (0.5%), Luhansk (0.4%) and Zakarpattia (0.3%) oblasts, with 77%, 33%, and 46%, respectively.

Changes to California Alfalfa Production and Perceptions during the 2011–2017 Drought

California experienced a severe multiyear drought stretching from 2011 through 2017, significantly reducing surface water supply for ecosystems, agriculture, and humans and prompting coordinated conservation efforts. Given that agriculture is the largest consumptive use of water in the state, one anticipated response to a severe drought would be to decrease production of low-value, high-water-use crops such as alfalfa. In this article we use a multimethod approach to examine both spatial distribution and public perceptions of alfalfa production in California over the course of the 2011 through 2017 drought. We find that although California alfalfa production did decline at the state level, it persisted and even increased in specific areas of the state. We also find that alfalfa persisted even though discourses and understandings that were critical of alfalfa production emerged in public forums during this time. We situate these findings within a broader context of California’s water management system, which meant that in practice, infrastructure and water rights allocation practices left many growers with little incentive to change growing practices, even in the face of serious meteorological drought.

Postmortem analysis of safe-yield estimation of a heterogeneous aquifer for rural water supply

Sustainable groundwater management is founded on the sound understanding of the effects of water extraction on the aquifer water level and the springs and streams receiving groundwater discharge. Pumping test data are commonly used in extraction licence applications to evaluate aquifer properties and assess the magnitude of storage depletion resulting from pumping. However, a short duration (eg 48 hours) pumping test can fail to detect the presence of aquifer boundaries, as the cone of depression is not large enough to reach the boundaries. This may cause an underestimation of long-term drawdown and an overestimation of permissible extraction rate (ie safe yield). In the rural town of Irricana in Alberta, groundwater extraction licences for municipal water supply wells were issued in the early 1980s based on the analysis of 48-hour pumping tests. Actual water extraction rates were substantially below the licensed rates, but the unanticipated and excessive drawdown in the aquifer forced the town to discontinue pumping and switch to surface water supply after 25 years. To examine the cause of overallocation, a new 48-hour pumping test was conducted in the same aquifer, which included an extended drawdown analysis using 26 days of recovery data. Geological formation logs for existing wells in the area surrounding Irricana were used to infer the extent of sandstone aquifer units within the heterogeneous bedrock formation. The new data analysis showed that the aquifer is semi-closed, contrary to the infinite-aquifer assumption used in the original pumping test, which caused additional drawdown due to the aquifer boundary effects. This study suggests an improved procedure for estimation of storage depletion using standard hydrogeological methods and readily available data. The new procedure provides a useful tool as part of adaptive groundwater management, in which water levels and other relevant variables are monitored and licensed extraction rates are adjusted accordingly.

Nash bargaining in a general equilibrium framework: The case of a shared surface water supply

We extend the axiomatic Nash bargaining approach to the context of interregional water sharing in order to assess the approach’s normative implications in a general equilibrium (GE) framework. The GE model is applied to a water development project proposed for the Wasatch Front and Cache Valley regions of Utah — the Bear River Development Project (BRDP). We demonstrate conceptually how an allocation rule and attendant net regional welfare measures are endogenously determined as equilibrium solutions to the bargaining problem. Numerical analysis, based upon a simulation model calibrated to current data, reveals that Nash bargaining is generally infeasible as a solution mechanism for sharing surplus water supplies generated through the implementation of the BRDP, with or without potential ex post side-payments made between Cache Valley and the Wasatch Front. Only in the special case of (1) larger future regional population sizes, (2) a hypothetical, joint per-capita cost-share arrangement where total project (i.e. fixed) costs are shared equally across the two regions, (3) hypothetically larger water augmentation rates, and (4) the ignoring of potential environmental costs, is the Nash bargaining solution viable. Otherwise, for all other scenarios where the analysis is based upon current or future population sizes, joint- or region-specific cost-share arrangements, lower or higher water augmentation rates, and internalized or externalized environmental costs, the Nash bargaining solution is found to be unattainable as a potential mechanism to share surplus water supplies produced by the BRDP.

Typification of Kherson region by water availability for irrigation and its environmental consequences

. The article presents the results of regional typification for the Kherson region by water availability for irrigation, taking into account the possible environmental risk as a result of the increase in irrigated area. The grouping of the territories previously differentiated by water availability into the following subtypes was performed: low rate of natural surface and groundwater water availability; sufficient rate of groundwater availability variously suitable for irrigation; high level of transit river flow availability; provided water supply of different quality from irrigation sources. Also, the territory grouping was made by the zones of ecological risk according to ecological and amelioration qualifications along with the separation of admissible ecological risk zones (potentially conditionally unstable areas with good ecological and reclamation conditions), zones of increased ecological or potentially unstable areas with the satisfactory and endangered condition), zones of sustainable ecological risk (potentially unstable areas with the unsatisfactory or very unsatisfactory land condition), zones of ecological crises development (potentially very unstable with the very unsatisfactory land condition). &#x0D; It was specified that within the Kherson region predominate the areas with low natural water supply from local surface flow in combination with the zones of increased ecological risk (Kakhovka irrigation zone) or with the zones of stable ecological risk (Oleksandrivska irrigation zone, Kalanchak irrigation system). Additional surface water supply for irrigation is provided by the main canals from the Kakhovka reservoir. Further increase in irrigation areas within these typological territories, on the one hand, can be provided with available resources on the other hand, may lead to deterioration of ecological and reclamation condition of irrigated land and aggravation of water and ecological situation, first of all, rising groundwater level.

3D printed nanofiltration membrane technology for waste water distillation

Surface water supply provides the vast majority of the world's drinkable water, however, surface water may contain a broad variety of pollutants originated from various sources, such as households, industry, and agriculture. As a result, it is critical to achieve acceptable water quality while also reducing the organic and inorganic impurities. Potable water production methods have been developed and tested in various ways. It is possible to manufacture high-quality drinking water using nanofiltration (NF) membranes. In contrast, fouling has remained the most significant barrier to membrane technology advancement. Renewable energy sources may decrease the extra energy needed by a membrane with tiny holes. Recent years have seen a significant increase in interest in three-dimensional printing (3D printing [3D-P]). Surface imprinting technologies, in general, have not yet reached the maturity stage of development, notably in membrane design and production. It is discussed in this review article how different 3D printing technologies are now accessible, how they relate to current breakthroughs in the area, and how they may be used to fabricate nanosheets, module spacers, or thin layers design for water purification as well as potential applications of surface imprinting in the near future. It is anticipated that the revolutionary synthesis of novel membrane module components will occur in the near future due to recent breakthroughs in 3D-P technology. It is predicted that 3D-P technologies would create a broader range of membrane module components with improved efficacy and efficiency due to speed, materials, and resolution improvements. Water purification methods comprising membrane separation are potential applications that might benefit from surface imprinting patterns with complicated topography in the future for water purification among them.

Calibration and Validation of Calcium Carbonate Precipitation Potential (CCPP) Model for Strontium Quantification in Cold Climate Aquatic Environments

The ability to robustly quantify the potential for strontium precipitation and scaling in both natural surface waters and water infrastructure systems is limited. In some regions, both surface and ground water supplies contain significant concentrations of naturally occurring radionuclides, such as strontium, that can accumulate in water, soils and sediments, media, and living tissues. Methods for quantifying and predicting the potential for these occurrences are not readily available nor have they been tested and calibrated to cold region aquatic environments. Through extensive literature review, it was determined that a modified calcium carbonate precipitation potential (CCPP) model offered a scientifically credible approach to filling that knowledge gap in both the science and engineering of strontium fate and transport in water. The results from previous field and laboratory experiments were compiled to not only elucidate the fate and transport of strontium in water systems, but also to calculate the logarithmic distribution coefficient, λ, for strontium under co-precipitation conditions. Lambda (λ) is both time- and water-quality sensitive and must be measured as water mixes from source to receiving environment to determine continuous loss of Sr from the water phase. The data were collected to develop the strontium precipitation potential model that can be used in surface water quality assessment. The tool was then applied to pre-existing, publicly available, and extensive datasets for several rivers in Saskatchewan, Canada, to validate the model and produce estimates for strontium precipitation potential in those rivers.

Impact of Participation in Groundwater Market on Farmland, Income, and Water Access: Evidence from Pakistan

Groundwater irrigation has a critical role in the sustainability of arable farming in many developing countries including Pakistan. Groundwater irrigation is generally practiced to supplement surface water supplies in Pakistan. Nevertheless, uninterrupted and extensive use of groundwater irrigation has raised several concerns about its sustainability and resultant environmental implications. Due to the scarcity of groundwater and heterogeneity in farmers’ resources, informal groundwater markets have emerged in Pakistan, where farmers trade water using a contractual system. Yet, the effects of these markets on agricultural productivity and equity remain largely unknown. This paper aims to analyze the impact of participation in the groundwater market on farmland utilization, cropping patterns, water access, and income. We analyze these impacts using primary data collected from 360 farmers in three different zones of the country’s largest province. The farmers were categorized as buyers, sellers, and self-users of water. Results indicate that participation in water markets increased agricultural land utilization, evinced by a higher cropping intensity among participants. A horizontal and vertical equity analysis of water markets shows that although large farmers have better access to groundwater irrigation, water market participation improves equity to water access. Based on income inequality measures such as the Gini coefficient and the Lorenz curve, water market participation also improves farmer incomes regardless of farm size. Propensity score matching revealed that wheat yield and income among water-market participants went up by approximately 150 kg and PKR 4503 per acre compared with non-participants. Groundwater market participants’ higher crop productivity and income level suggest that water markets need a thorough revisit in terms of policy focus and institutional support to ensure sustainable rural development.

Streamflow reconstructions from tree rings and variability in drought and surface water supply for the Milk and St. Mary River basins

The Milk and St. Mary Rivers are international waterways straddling the United States and Canada and traversing four Tribal Nations before draining into the Missouri and South Saskatchewan Rivers respectively. Management of water resources in the region is challenged by the complexity of stakeholder interests, the limitations of existing management infrastructure, and by a limited characterization of the long-term streamflow and hydroclimatic variability across the area. We used existing records of natural streamflow to investigate the relationships between seasonal climate variability and differences in the timing and volume of flow from the headwaters to the prairie tributaries. Then, using a network of tree-ring chronologies to reconstruct records of past streamflow, we assessed whether drought risk relates to these sub-basin specific differences and if drought events experienced during the observational period are representative of those that have occurred over the long-term. Observed climate-flow relationships suggest that outside of the mountain headwaters, where precipitation dominates the hydrograph, streamflow variability on lower reaches of the Milk River is particularly sensitive to winter temperatures. This sensitivity was reflected by severe drought conditions over the prairies during the 2000s, implying potentially large future flow reductions with warming. The streamflow reconstructions show sub-basin specific drought risks that also imply greater temperature driven drought severities across the prairie tributaries. Within the mountain and foothill sub-basins numerous past drought episodes exceed the magnitude and duration of observational period events, which implies the potential for future water supply management challenges stemming from severe, long-duration droughts coupled with the negative hydrologic effects of warmer temperatures.

Optimization of cropping pattern under seasonal fluctuations of surface water using multistage stochastic programming

Abstract Given rapid socio-economic development, increasing food demand and decreasing available resources, the challenge of seasonal fluctuations of surface water has become a major problem in the agricultural sector, causing a change in consumption from surface water to groundwater resources and reduction of farmers' income. Therefore, optimal programming of the cropping pattern is necessary to handle such challenges. To accomplish this aim, a model of irrigation water allocation was developed based on cropping pattern using multistage stochastic programming in accordance with surface water supply fluctuations. In this model, different stochastic states were considered for all irrigation seasons in the irrigation network of the Jiroft plain in Kerman Province, Iran, which faces a severe shortage of surface water resources and the tendency of farmers to overuse groundwater resources. By solving a multistage stochastic model, it can be observed that, by utilizing an appropriate programming of the cropping pattern, more benefits for the farmers could be realized in the conditions of available surface water fluctuations. The results also indicated that if the surface water released into the canals increased in the spring, the share of profitable high water consumption crops in the pattern will increase, which will strengthen farmers' profits and put pressure on groundwater resources. However, this could not be expected to lead to a significant reduction of groundwater resource consumption and a significant increase of cropping intensity. According to the results obtained, surface water resources cannot meet the water needs of the region, even by using optimal cropping patterns, and this has led to overuse of groundwater resources in this area. Finally, such planning can help adoption of desired policies for irrigation water management through the proper release of these resources.

Electrochemical Reduction and Voltammetric Sensing of Lindane at the Carbon (Glassy and Pencil) Electrodes

In the agricultural field, pesticides are used tremendously to shield our crops from insects, weeds, and diseases. Only a small percentage of pesticides employed reach their intended target, and the remainder passes through the soil, contaminating ground and surface-water supplies, damaging the crop fields, and ultimately harming the crop, including humans and other creatures. Alternative approaches for pesticide measurement have recently received a lot of attention, thanks to the growing interest in the on-site detection of analytes using electrochemical techniques that can replace standard chromatographic procedures. Among all organochlorine pesticides such as gamma-lindane are hazardous, toxic, and omnipresent contaminants in the environment. Here, in this review, we summarize the different ways of the gamma-lindane detection, performing the electrochemical techniques viz cyclic, differential, square wave voltammetry, and amperometry using various bare and surface-modified glassy carbon and pencil carbon electrodes. The analytical performances are reported as the limit of detection 18.8 nM (GCE–AONP–PANI–SWCNT), 37,000 nM (GCE), 38.1 nM (Bare HBPE), 21.3 nM (Nyl-MHBPE); percentage recovery is 103%.

Geothermal water in Bakreshwar-Tantoli region in West Bengal, India: Implications on water quality for irrigation and drinking purposes

Groundwater becomes more critical for drinking and irrigation purposes due to reduced surface water supplies and contamination of these sources. Knowing the quality of underground water is vital to the protection of public health and sustainable water resource development. The goal of this study is, therefore, to assess the suitability of groundwater for drinking and irrigation purposes in the Bakreshwar-Tantaloi hot springs in West Bengal, India. This study evaluates the quality of water produced from 7 different geothermal hot springs by investigating its chemical concentration. The physicochemical parameters were examined for the water samples. The suitability of groundwater for drinking purposes was measured by contrasting the chemical concentrations with the WHO standards and also computing and comparing the Water Quality Index (WQI) value with recommended norms. The concentrations of Ca2+, Mg2+, Cl−, SO42−, and NO3− are within the WHO (2011) and BIS (2012) tolerable limit. Statistical analyses are used to reveal patterns and groups from the physiochemical dataset of groundwater samples. Principal Component Analysis (PCA) and factor analysis identify the source for groundwater parameters. The correlation matrix and scatter plot matrix give the relationship among major chemical ions of water samples. Dendrogram defines the relationship between physicochemical variables and groups them into strong to weak correlations among water components.

EVALUATION OF SPATIAL AND TEMPORAL HYDROLOGICAL DROUGHT USING SURFACE WATER SUPPLY INDEX IN MALEWA RIVER CATCHMENT, NAIVASHA

There has been a critical problem of the devastating natural hazard (hydrological drought) which greatly affects a significant proportion of the large population particularly those living in arid and semi-arid areas. The flow regime of the Malewa River is reducing due to the river fluctuation, increasing scarcity of water during dry periods. The purpose of this research was to assess spatial and temporal hydrological drought using Surface Water Supply Index (SWSI) at Malewa River catchment. The data were based on hydro-meteorological data which included rainfall, level of water at Lake Naivasha, and streamflow of Malewa River for the years 1980-2018. They were obtained from Water Resources Authority (WRA) in Naivasha and Kenya Meteorological Department (KMD) in Nairobi, Kenya. The field data were first normalized to have all input attributes temporary variables with their distribution having zero means and a standard deviation of 1. Later the normalized data were calculated using basin-calibrated algorithm of SWSI to determine the hydrological condition. In SWSI, the highest percentage of classification for the stations were near the average of -0.9 to 1.0, with 34% for the Malewa area and 30% for the Turasha area. In spatial distribution analyses, hydrological drought severity was highest along the southern part of the catchment and lowest along with Eastern and North-Eastern areas. Therefore, hydrological drought severity was experienced in the catchment in terms of temporal and spatial analyses and increased along the flow path of the river. Hydrological drought assessment shows a technical manner for a comprehensive understanding of drought offering proper mitigation strategies and plan to control this natural disaster.

Identifying Spatial Patterns of Hydrologic Drought over the Southeast US Using Retrospective National Water Model Simulations

Given the sensitivity of natural environments to freshwater availability in the Southeast US, as well as the reliance of many municipal and commercial water consumers on surface water supplies, specific issues related to low river streamflow are apparent. As a result, the need for quantifying the spatial distribution, frequency, and intensity of low flow events (a.k.a., hydrologic drought) is critical to define areas most susceptible to water shortages and subsequent environmental and societal risk. To that end, daily mean discharge values from the National Water Model (NWM) retrospective data (v. 2.0) are used to assess low flow frequency, intensity, and spatial distribution within the Southeast US. Low flow events are defined using the US EPA 7Q10 approach, based on the flow duration curve (FDC) developed using a 1993–2018 period of record. Results reflect the general climatological patterns of the region, with a higher probability of low flow events occurring during the warm season (June–August) while low flow events in the cool season (January–March) are generally less common and have a higher average discharge. Spatial analysis shows substantial regional variability, with an area from southeastern Mississippi through central South Carolina showing higher low flow event frequency during the cool season. This same area is also highlighted in the warm season, albeit along a more expansive area from central Alabama into the piedmont region of North Carolina. Results indicate that the NWM retrospective data are able to show general patterns of hydrologic drought across the Southeast US, although local-scale assessment is limited due to potential issues associated with infiltration and runoff during periods of warm-season convective rainfall.