•Scientific framework is developed for assessing e-flow for highly regulated and data-scarce rivers.•Profound alteration in river flow regimes due to water infrastructure and diversions.•For ‘low’ ...and ‘moderate’ alteration scenarios, about 50–60% and 22–30% of the natural flow is needed as e-flow.•The outcome of the study is useful for judicious water allocation while mitigating the human-induced impacts on riverine ecosystem.•The study can be replicated to other hydro-climatic regions under data scarcity condition.
For mitigating human-induced river alterations and reviving the dying rivers to preserve natural ecosystem services, the assessment of environmental flow (e-flow) is essential. However, e-flow estimation under data-scarce conditions for the rivers being heavily regulated has become a major issue worldwide under changing environmental conditions, particularly in developing countries. To address this challenge, this study was carried out for estimating time-varying e-flows for a heavily regulated river of Eastern India under data-scarce conditions. In the absence of any pre-impact streamflow data and tributary inflow to the main river reach, this study proposes a framework integrating three methods to estimate e-flow for river reaches. A hydrologic model (first method) was employed to estimate tributary inflows to the main river, which was used in the mass-balance based naturalization approach (second method) for reconstructing the daily long-term natural streamflow from the observed post-impact streamflows at two gauging stations on the main river. Thereafter, the naturalized streamflow was used for estimating e-flows by the GA optimization technique (third method) for two pragmatic scenarios (‘Low Hydrologic Alteration’, and ‘Moderate Hydrologic Alteration’) at the two stations. Analysis of the results revealed that the major impounding and diversion infrastructures built on the river have caused profound alteration to the river reach having an overall degree of hydrologic alteration index greater than 70. The mean post-impact streamflows tend to vary less and have decreased by 35–50 % with 2–3 times reduction in the peak flow as compared to the pre-impact condition. The estimated monthly e-flows for the river basin range from 1.2 to 185 m3/s (50–60 % of the natural flow) and 0.5 to 80 m3/s (22 to 30 % of the natural flow) for the ‘Low’ and ‘Moderate’ alteration scenarios, respectively. Results of this study can aid in formulating efficient strategies for sustainable water resources management in the river basin.
Conventional agricultural practices that rely heavily on blanket fertilizer recommendation, eventually leading to deteriorated partial factor productivity and N use efficiency. We investigated the ...effect of SPAD-based N-management on productivity and N use efficiency of rice and wheat in eastern India. Here, in the experiment three SPAD thresholds (34, 36 and 38 in rice and 38, 40 and 42 in wheat) using three N levels (15, 25 and 35 kg N ha
−1
) in split were incorporated as real-time N management (RTNM), one fixed-time N management (FTNM), farmers' fertilizer practice (FFP) and control (No fertilizer) were introduced in wet and dry seasons for rice and wheat, respectively, during the years 2010 to 2012. Topdressing with 25 kg N ha
−1
at medium SPAD (S
36
in rice and S
40
in wheat) increased soil N availability, leaf N content and grain yield of rice (5215 kg ha
−1
) and wheat (4483 kg ha
−1
) over the grain yield recorded under a low rate of N topdressing at low SPAD. While saving 33.3% N in rice and 18.8% N in wheat, the agronomic N use efficiency (58.5% in both rice and wheat) and nitrogen recovery efficiency (32.2% in rice and 15.1% in wheat) can be increased when compared with conventional FTNM. The SPAD-based management strategy showed great promise in efficient management of N fertilizer, and we estimated the optimal SPAD threshold for rice and wheat as 37.5 and 41.8, respectively.
Increasing groundwater contamination across the globe triggered the concept of “aquifer vulnerability”, which has been extensively used worldwide during past three to four decades by researchers and ...policy makers for protecting groundwater from pollution. However, only a few recent studies have focused on the performance evaluation of two or more vulnerability assessment methods. Some of these studies have resulted in contrasting findings. Given this fact and considering growing threat of groundwater contamination due to increasing human activities across the globe, it is necessary to critically review existing methods, understand current research trends, and identify major challenges associated with the assessment of aquifer vulnerability. Hence, the aim of this study is to present a comprehensive review of the methods and approaches used for the evaluation of aquifer vulnerability for ‘resource’ and ‘source’ protection. First, the concept and types of aquifer vulnerability along with the definitions evolved over the years are presented, and then the methods for assessing aquifer vulnerability are suitably classified and briefly discussed. Second, the concept of vulnerability assessment for ‘source’ protection is highlighted, and the evolution of groundwater vulnerability evaluation methods is presented with an enlightening block diagram. Third, current research trends and critiques on past studies are discussed. Fourth, the major challenges of vulnerability assessment are highlighted and a way forward is suggested. It is concluded that the progress of vulnerability evaluation methods has not kept pace with the advancement of knowledge and tools/techniques. There is an urgent need for developing a scientifically robust and somewhat versatile methodology for the evaluation of ‘intrinsic’ and ‘specific’ groundwater vulnerability for ‘resource’ and ‘source’ protection under varying hydrogeologic and hydro-climatic conditions. It is emphasized that more studies should be devoted to vulnerability assessment for ‘source’ protection using ‘Source-Pathway-Receptor/Target’ approach. Also, spatial decision support systems should be developed using modern tools/techniques including artificial intelligence to improve decision-making process for protecting vital groundwater resources.
•This study presents a review of methods used for mapping of groundwater vulnerability to pollution.•Methods widely used for assessing aquifer vulnerability are classified into suitable groups and their overview is provided.•We illustrated evolution of groundwater vulnerability methods by an enlightening block diagram, and methods are critiqued.•Future challenges are identified and a way forward is suggested.•This study emphasizes need of a robust and versatile method using modern tools for groundwater vulnerability evaluation.
Groundwater is a precious natural element which ensures global water, food, and environmental security in the twenty-first century. Systematic monitoring, sustainable utilization, preservation and ...remediation are critical aspects of efficient groundwater resource management. This study deals with the analysis of spatial variability and trend in groundwater chemistry as well as identification of possible contamination sources in a coastal alluvial basin of eastern India. Pre-monsoon season data of 14 groundwater-quality variables measured in ‘leaky confined’ and ‘confined’ aquifers were analyzed for ten years (2012–2021). Mann–Kendall (M–K) test with the Sen’s Slope Estimator, Spearman Rank Order Correlation (SROC) and Innovative Trend Analysis (ITA) tests were employed to assess decadal (2012–2021) trends. The analysis of the results indicated that the ‘critical’ water-quality parameters exceeding the acceptable limits for drinking are TDS, EC, TH, pH, Mg
2+
, Na
+
, K
+
, Fe
2+
, HCO
3
ˉ, Clˉ and NO
3
ˉ. Weak negative correlations between rainfall and groundwater elevation for both the aquifers reveal poor rainfall recharge into the aquifers. Therefore, a reduction in groundwater abstraction and augmentation of groundwater recharge is recommended. Trend analysis results indicated that the concentrations of TH, Mg
2+
and Fe
2+
exhibit significant increasing trends in the ‘leaky confined aquifer’. In contrast, significant rising trends in TH, Mg
2+
, Na
+
, Fe
2+
, HCO
3
ˉ and NO
3
ˉ concentrations are identified in the ‘confined aquifer’. Further, the SROC test could not detect the trends in groundwater quality in most blocks and for many parameters. On the other hand, the ITA test revealed significant trends in most of the parameters of the two aquifers in almost all the blocks. Trend magnitudes of the groundwater-quality parameters based on the Sen’s Slope Estimator and the ITA test vary from –63.7 to 58.65 mg/L/year for TDS, –14 to 39.07 mg/L/year for TH, –1.49 to 4.83 mg/L/year for Mg
2+
, –7.14 to 22.96 mg/L/year for Na
+
, –0.32 to 0.44 mg/L/year for Fe
2+
, –8.33 to 20.75 mg/L/year for HCO
3
ˉ, –26.52 to 31.01 mg/L/year for Clˉ and 1.29 to 3.76 mg/L/year for NO
3
ˉ over the study area. The results of M–K and ITA tests were found in agreement in all the blocks for both the aquifers. Groundwater contamination in both the aquifers can be attributed to weathering, geogenic processes, mineral dissolution, seawater intrusion, poor recharge pattern and injudicious anthropogenic activities. It is strongly recommended that concerned authorities urgently formulate efficient strategies for managing groundwater quality in the ‘leaky confined’ and ‘confined’ aquifers which serve as vital sources of drinking and irrigation water supplies in the study area.
Groundwater is a vital source of freshwater in both urban and rural regions of the world. However, its injudicious abstraction and rapidly increasing contamination are posing a severe threat for ...sustainable water supply worldwide. Geographical Information System (GIS)-based groundwater quality evaluation using Groundwater Quality Index (GQI) has been proved to be a cost-effective tool for assessing groundwater quality and its variability at a larger scale. However, the conventional GQI approach is unable to deal with uncertainties involved in the assessment of environmental problems. To overcome this limitation, a novel hybrid framework integrating Fuzzy Logic with the GIS-based GQI is proposed in this study for assessing groundwater quality and its spatial variability. The proposed hybrid framework is demonstrated through a case study in a hard-rock terrain of Southern India using ten prominent groundwater-quality parameters measured during pre-monsoon and post-monsoon seasons. Two conventional GIS-based GQI models GQI-10 (using all the ten groundwater-quality parameters) and GQI-7 (using seven ‘concerned/critical’ groundwater-quality parameters) as well as hybrid Fuzzy-GIS-based GQI (FGQI) models (using seven critical parameters) were developed for the two seasons and the results were compared. The Trapezoidal membership functions classified the model input parameters into ‘desirable’, ‘acceptable’ and ‘unacceptable’ classes based on the experts’ knowledge and water quality standards for drinking purposes. The concentrations of Ca2+, Mg2+, and SO42− in groundwater were found within the WHO desirable limits for drinking water throughout the year, while the concentrations of seven parameters (TDS, NO3−-N, Na+, Cl−, K+, F− and Hardness) exceed their permissible limits during pre-monsoon and post-monsoon seasons. A comparative evaluation of GQI models revealed that the FGQI model predicts groundwater quality better than the conventional GQI-10 and GQI-7 models. GQI modeling results suggest that the groundwater of most of eastern and southern parts (∼60% in pre-monsoon season; ∼90% in post-monsoon season) of the study area is unsuitable for drinking. Further, the groundwater quality deteriorates during post-monsoon seasons compared to pre-monsoon seasons, which indicates an increased influx of contaminants from different industries, mining areas, waste disposal sites and agricultural fields during monsoon seasons. This finding calls for the strict enforcement of regulations for proper handling of effluents from various contamination sources in the study area. It is concluded that the fuzzy logic-based decision-making approach (FGQI) is more reliable and pragmatic for groundwater-quality assessment and analysis at a larger scale. It can serve as a useful tool for the water planners and decision makers in efficiently monitoring and managing groundwater quality at watershed or basin scales.
Display omitted
•Novel hybrid framework integrating Fuzzy Logic with GIS-based GQI is developed.•FGQI is more reliable and useful for water-quality evaluation at larger scales.•Groundwater polluted zones are in eastern and southern parts of the study area.•Groundwater quality in post-monsoon seasons is worse than in pre-monsoon seasons.•Comprehensive strategies for sustainable groundwater management are urgently needed.
Water-saving production technologies are essential for increasing agricultural production under limiting water resources in future periods. Potato, the underground crop needs efficient soil and water ...management for production sustainability. Field experiments were conducted during the dry season of 2018–19 and 2019–20 to study the effect of rice straw mulch with drip irrigation on soil temperature and moisture content and thereby its effect on the potato yield and water productivity in subtropical India. Potato was grown with two levels of soil management (straw mulch and non-mulch) and four levels of water management, i.e., conventional furrow irrigation and drip irrigation up to full field capacity (100%FC), 90%FC, and 80% FC. The results stated that the straw mulch increased the soil temperature by 0.22–0.90 °C compared to non-mulch plots and the maximum increase was when the air temperature was lowest during the growing period. The straw mulch also increased the soil moisture content (+3.6%) and lowered evapotranspiration (9–14%) compared to the non-mulch. Similar to mulching, the limited drip irrigation (90%FC) increased the soil temperature by ≥ 2 °C as compared to furrow irrigation. The straw mulching effectively increased the tuber yield (+15%) under limited drip irrigation with 90%FC, but not in conventional irrigation. Integration of mulching with limited drip irrigation saved 42–58% irrigation water compared to conventional furrow irrigation without mulch. Straw mulching in drip-irrigated treatments significantly increased the water productivity (30–39%) compared to non-mulch. This study provides a reference point for policymakers that drip irrigation with straw mulch can be a feasible adaptation strategy for increasing potato production in subtropical locations under resource-limited environment.
•Mulching with drip irrigation improved the soil microclimate for potato productivity.•Straw mulching was better effective under drip irrigation than furrow irrigation.•Straw mulching with drip irrigation saved up to 58% water while improving potato yield.•Straw mulching with limited drip irrigation improved potato yield by 15%.•Drip irrigation increased marketable tuber grade potato production up to 30%.
This study investigated trends in 35 years (1979–2013) temperature (maximum, T
max
and minimum, T
min
) and rainfall at annual and seasonal (pre-monsoon, monsoon, post-monsoon, and winter) scales for ...31 grid points in a coastal arid region of India. Box-whisker plots of annual temperature and rainfall time series depict systematic spatial gradients. Trends were examined by applying eight tests, such as Kendall rank correlation (KRC), Spearman rank order correlation (SROC), Mann-Kendall (MK), four modified MK tests, and innovative trend analysis (ITA). Trend magnitudes were quantified by Sen’s slope estimator, and a new method was adopted to assess the significance of linear trends in MK-test statistics. It was found that the significant serial correlation is prominent in the annual and post-monsoon T
max
and T
min
, and pre-monsoon T
min
. The KRC and MK tests yielded similar results in close resemblance with the SROC test. The performance of two modified MK tests considering variance-correction approaches was found superior to the KRC, MK, modified MK with pre-whitening, and ITA tests. The performance of original MK test is poor due to the presence of serial correlation, whereas the ITA method is over-sensitive in identifying trends. Significantly increasing trends are more prominent in T
min
than T
max
. Further, both the annual and monsoon rainfall time series have a significantly increasing trend of 9 mm year
−1
. The sequential significance of linear trend in MK test-statistics is very strong (
R
2
≥ 0.90) in the annual and pre-monsoon T
min
(90% grid points), and strong (
R
2
≥ 0.75) in monsoon T
max
(68% grid points), monsoon, post-monsoon, and winter T
min
(respectively 65, 55, and 48% grid points), as well as in the annual and monsoon rainfalls (respectively 68 and 61% grid points). Finally, this study recommends use of variance-corrected MK test for the precise identification of trends. It is emphasized that the rising T
max
may hamper crop growth due to enhanced metabolic-activities and shortened crop-duration. Likewise, increased T
min
may result in lesser crop and biomass yields owing to the increased respiration.
In this study, 43-year (1965–2007) monthly and annual rainfall time series of ten rainfall stations in a semi-arid region of western India are analyzed by adopting three tests for testing normality ...and by applying autoregressive technique for exploring persistence. Gradual trends are identified by three tests, and their magnitudes are assessed by the Sen’s slope estimator. Also, abrupt changes are detected by using four tests and they are further confirmed by two tests. Box-whisker plots revealed that the rainfalls of June and September are right skewed for all the stations. The annual rainfalls of Bhinder, Dhariawad, and Gogunda stations are found considerably right skewed. The normality tests indicated that the rainfall of July does not deviate from the normal distribution at all the stations. However, the annual rainfall is found non-normal at five stations. The monthly rainfalls of June, July, and August have persistence respectively at three (Mavli, Salumber, and Sarada), two (Kherwara and Sarada), and one (Mavli) stations, whereas the annual rainfall has persistence at Girwa and Mavli stations. Significantly increasing trend is detected at Mavli in the rainfall of July and in the annual rainfall (
p
value > 0.05), while the negative trend in August rainfall at Dhariawad is found significant (
p
value > 0.10). This study revealed that the presence of serial correlation does not affect the performance of the Mann-Kendall test. Mean values of trend magnitudes for the rainfalls of June, July, August, and September are 0.3, 0.8, −0.4, and 0.4 mm year
−1
, respectively, and the overall mean value for the annual rainfall is 0.9 mm year
−1
. It is found that the standard normal homogeneity test and the Pettitt test are biased towards the end of the series to locate a change point. Conversely, the Bayesian test has a tendency to look for a change point in the beginning of time series. Confirmed abrupt changes in the rainfall time series are found in the year 2003 (Bhinder) in June; years 1974 (Mavli) and 1989 (Dhariawad and Salumber) in July; years 1972 (Sarada), 1990 (Dhariawad), and 2003 (Mavli) in August; years 1977 (Dhariawad), 1991 (Sarada), and 2004 (Kotra) in September; and in the year 1972 (Mavli and Sarada stations) in the annual series. It is emphasized that the significantly increasing trend of rainfall may have linkages with climate change and/or variability. Finally, this study recommends use of multiple statistical tests for analyzing hydrologic time series in order to ensure reliable decisions.
Climate change is one of the most important global environmental challenges, which affects the entire earth system in terms of negative impacts on food production, water supply, health, livelihood, ...energy, etc. The intent of the present study was to assess the impact of climate change on the water balance components of a data-starved Upper Baitarani River basin of Eastern India using ArcSWAT model. The ArcSWAT model was calibrated using SUFI-2 technique. The daily observed streamflow data from 1998 to 2003 were employed for calibration and those for 2004–2005 for validation. The calibration results were found to be satisfactory with the Nash-Sutcliffe efficiency (NSE) and mean absolute error (MAE) of 0.88 and 9.70 m
3
/s for the daily time step, respectively. Also, the model was validated successfully for simulating daily streamflow (NSE = 0.80 and MAE = 10.33 m
3
/s). The calibrated and validated model was then used to evaluate basin response to the anticipated climate changes by the end of the 21st century. Twelve independent as well as twenty eight combined area-specific climatic scenarios were considered in this study to evaluate the impact of climate change on the hydrology of the basin. The analysis of model results for the 12 Independent Climatic Scenarios indicated a reduction in the surface runoff ranging from 2.5 to 11 % by changing the temperature from 1 to 5 °C, whereas the increase in rainfall by 2.5 to 15 % suggested an increase in surface runoff by 6.67 to 43.42 % from the baseline condition. In case of 28 Combined Scenarios compared to the baseline condition, the changes in surface runoff would vary from −4.55 to 37.53 %, the groundwater recharge would change from −8.7 to 23.15 % and the evapotranspiration would increase from 4.05 to 11.88 %. It is concluded that future changes in the climatic condition by the end of the 21st century are most likely to produce significant impacts on the streamflow in the study area. The findings of this study and those of follow-up studies in this direction will be useful for guiding suitable adaptation measures for sustainable water management in the basin in the face of impending climate change.
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