Rashid Mahmood | University of Chinese Academy of Sciences (original) (raw)

Papers by Rashid Mahmood

The water resources of the Chari River basin, contributing more than 90% of the water to one of t... more The water resources of the Chari River basin, contributing more than 90% of the water to one of the largest lakes in Africa, known as Lake Chad, are highly vulnerable to natural and anthropogenic changes. Therefore, the changes in water resources were predicted for the next 20 years (i.e., 2016–35) by using the harmonic regression model (HRM), one of the most sophisticated time series methods, and also projected under representative concentration pathways (RCPs) by using the multimodel approach for the periods 2021–50, 2051–80, and 2081–2100, with respect to the baseline period (1971–2001). The Tropical Rainfall Measuring Mission (TRMM), Climatic Research Unit (CRU), and dynamically downscaled climatic data were used in the analysis of the present study. The results showed that under MME-RCP2.6 (multimodel ensemble of RCMs), low flow (average of low-flow months, December–July), high flow (August–November), and annual flow were projected to decrease in the future. In contrast, under MME-RCP4.5 and MME-RCP8.5, high and annual flows were projected to increase in all three time horizons, while low flow will decrease except in 2021–50 under MME-RCP8.5. In the next two decades, the HRM showed decrease in all type of flows (low, high, and annual), very similar to the results under MME-RCP2.6 for the same period. In contrast, almost all flows are expected to increase under MME-RCP4.5 and MME-RCP8.5 in the next two decades. On the whole, the flows are expected to decrease under the HRM and RCP2.6 but to increase under RCP4.5 and RCP8.5.

Recent evidence of regional climate change impacts on hydrological cycle directed us to study the... more Recent evidence of regional climate change impacts on hydrological cycle directed us to study the floods in a high elevated and rapidly urbanized river basin, the Kabul River basin (KRB), Pakistan, which is susceptible to frequent flooding. Therefore, we analyzed the changes in flood regime at various spatial and temporal scales and their possible causes, which is accomplished by using flood indicators, trend analysis, change point analysis, and hydrological modeling. The results showed that the northern and northwestern parts of the KRB were more exposed to flood hazard than the southern parts under long-term scenario (1961/64-2015). However, after the change points, the flood risk decreased in the northern and increased in the southern regions. This spatial shift increased the vulnerability of population to the flood hazard, because the majority of population resides in the southern region. The extreme precipitation has also increased, especially the maximum one-day rainfall and maximum five-day rainfall throughout the basin. Particularly, the major cause of the decrease in different flood indicators in the northern parts of the KRB is the corresponding decrease in the annual and monsoonal rainfall and corresponding positive mass balance of glaciers in the northern region after the occurrence of change point in flood regime. However, the major cause of the increase in flood hazard on the southern part of the KRB is associated with maximum five-day rainfall. A 68% variability of annual maximum flood for the Kabul River at Nowshera and an 84% variability of annual maximum flood for Bara River at Jhansi post are explained by maximum five-day rainfall. In addition, a considerable decrease in forests (–5.21%) and increase in the urban area (88.26%) from 1992–2015 also amplifies the risk of higher flood peaks. The results of hydrological modeling suggest that the six-hourly flood peak increased by 6.85% (1992–2010) and 4.81% (2010–2015) for the extreme flood of 2010 for the Kabul River at Nowshera. The flood peak per decade will increase by 8.6%, as compared to the flood peak under the land use scenario of 2010. Therefore, consideration of proper land use planning is crucial for sustainable flood management in the KRB.

The objective of the study was to configure the Hydrological Modeling System (HEC-HMS) in such a ... more The objective of the study was to configure the Hydrological Modeling System (HEC-HMS) in such a way that it could simulate all-important hydrological components (e.g., streamflow, soil moisture, snowmelt water, terrestrial water storage, baseflow, surface flow, and evapotranspiration) in the Three-River Headwater Region. However, the problem we faced was unsatisfactory simulations of these hydrological components, except streamflow. The main reason we found was the auto-calibration method of HEC-HMS because it generated irrational parameters, especially with the inclusion of Temperature Index Method and Soil Moisture Accounting (an advanced and complex loss method). Similar problems have been reported by different previous studies. To overcome these problems, we designed a comprehensive approach to estimate initial parameters and to calibrate the model manually in such a way that the model could simulate all the important hydrological components satisfactorily.

The hydrological extremes like floods and drought are increasing in recent decades all over the w... more The hydrological extremes like floods and drought are increasing in recent decades all over the world but particularly in
South Asia. Pakistan ranked 5th most vulnerable as per the climate risk index because it is susceptible to floods and droughts
across various spaces and times. The recent evidence of climate change led us to study the floods for a high-altitude river
basin, the Kabul River basin (KRB), Pakistan. The region is customarily influenced by flooding. Accordingly, the study was
planned to examine the most likely impact of climate change on extreme floods under high-end warming scenario RCP 8.5.
The multi-model ensemble from CMIP5 along with HEC-HMS was employed to quantify the impact of climate change on
extreme floods. The main research results represented that the projected flood magnitude has been decreased in the future
period (2016–2100) as compared to the historical period (1981–2015), for the Kabul River at Nowshera under RCP 8.5.
The floods of 2, 5, 10, 25, 50, and 100 years are projected to be decreased by 2%, 24%, 23%, 16%, 11%, and 17% respec-
tively. The magnitude of 3-day rainfall events of all durations is projected to decrease throughout the basin. Therefore, the
corresponding magnitude of extreme flood events will also decrease in the KRB, Pakistan. However, the frequency of the
3-day rainfall events of 2, 5, and 10 years return period has been increased in the future period (2016–2100) as compared
to the historical period (1981–2015). This frequent occurrence of extreme rainfall events can be challenging to mitigate the
flood hazard. The findings of the study will be vital to improving flood management under changing climate in the region.

The Amudarya River (ADR) is the largest source of freshwater in Central Asia providing livelihood... more The Amudarya River (ADR) is the largest source of freshwater in Central Asia providing livelihood to millions of people by extracting water for agriculture. However, the over-exploitation has created some critical environmental issues. For example, almost no water for the delta and the Aral Sea, which was once the 4th largest lake in the world. The present study focused on the assessment of environmental flow requirements (E-flows) in the basin. However, the main challenges in the accomplishment were the unavailability of natural streamflow, which is necessary for E-flow assessment, and sparse and limited hydroclimatic data. A hydrologic model was configured to simulate naturalized streamflow using the meteorological data from the Climate Research Unit. Four hydrological methods (i.e., Tennant, low flow index (7Q10), flow duration curve analysis (Q90, and Q95), and flow duration curve shifting (FDCS)) and all-method mean were applied to estimate E-flows at 34 sites on all tributaries of the ADR. According to FDCS, 7Q10, Q90, and Q95, E-flows should be 46%, 37%, 30%, and 25% of naturalized mean annual flow (NMAF), respectively, and on average, it should be 35% of NMAF, assessed by the all-methods mean. For low-flow (October–March) and high-flow (April–September) months, E-flows were determined to be 20–30% and 40–98% of NMAF, respectively. E-flow evaluation with the current environmental conditions showed very serious concerns because no sites met the environmental flow requirements below Kerki. This study will be guidelines to improve the riverine ecosystem and for future sustainable development in the region.

Environmental flows (EFs), essential for upholding the ecological integrity of rivers and aquatic... more Environmental flows (EFs), essential for upholding the ecological integrity of rivers and aquatic habitats, have been disrupted significantly by diverting water for agricultural, industrial and domestic uses. This underscores the imperative of implementing sustainable water resource management to harmonize agricultural and environmental needs. The study was conducted in the Indus River Basin (IRB), a region extensively transformed by human interventions. EFs were determined through various techniques, including the flow duration curve shifting method, flow duration curve analysis, low-flow indices, the Tennant method, the Smakhtin approach, the Tessmann method and the Pastor method. Analysing the estimated EFs alongside downstream flows unveiled specific timeframes (days, months and seasons) of unmet EF requirements. To safeguard the downstream ecosystems, the following EFs were estimated for the respective locations: 880 m3/s (38% of the mean annual flow [MAF]) for the Indus River at Tarbela Dam, 412 m3/s (48% of the MAF) for the Jhelum at Mangla Dam, 425 m3/s (44% of the MAF) for the Chenab at Marala headworks, 389 m3/s (56% of MAF) for the Ravi at Balloki headworks, 184 m3/s (50% of MAF) for the Sutlej at Sulemanki headworks and 231 m3/s (38% of MAF) below Kotri Barrage. The study revealed that violations of EFs occurred 41%, 43%, 44% and 52% of the time during the study period for the Chenab at Marala headworks, the Ravi at Balloki headworks, the Sutlej at Sulemanki headworks and the Indus River at the Kotri Barrage, respectively. The results highlighted that the Chenab, Ravi and Sutlej rivers are particularly susceptible to vulnerability, as the estimated EFs were not consistently upheld in these rivers. These findings underscore the urgent need to take appropriate measures to ensure EFs are not violated, thus safeguarding the downstream ecosystems.

Earth’s average air temperature is warming at a substantial rate leading to an increase in the fr... more Earth’s average air temperature is warming at a substantial rate leading to an increase in the frequency and severity of extremes with major
environmental and socio-economic impacts. The present study discusses temperature and precipitation extremes in Kashmir Valley using
observational data from six meteorological stations. An Expert Team on Climate Change Detection and Indices (ETCCDI) (http://etccdi.paci-
ﬁcclimate.org/) provides 25 extreme climate indices (15 for temperature and 10 for precipitation) to be used. The absolute extreme
temperature indices (TXx, TXn, TNx, and TNn) exhibit increasing tendencies, according to the ﬁndings. The number of changes witnessed
in daily maximum temperature was greater than the daily minimum temperature which was manifested by increasing diurnal temperature
range (DTR; 0.012 °C/year). These changes in extremes have impacts that pose a threat to agriculture, snow day and cover, glaciers, water
resources, ecosystem services, etc. of the study region. The region is undergoing signiﬁcant urban and land system changes making it further
vulnerable to natural hazards. The ﬁndings are expected to further augment the hazard and risk analysis and the necessary disaster risk
reduction measures for climate-related disasters in the region. These analyses will be helpful for the development of strategies for climate
risk management in Kashmir.

Article, 2024

Himalaya – one of the pristine and ecologically fragile mountain ecosystem is highly vulnerable t... more Himalaya – one of the pristine and ecologically fragile mountain ecosystem is highly vulnerable to any small changes in
climatic system. Under changing climate conditions, assessing regional trends become more important owing to depen-
dence of more than 1 billion people on Himalayas. To analyze the climatic trends and magnitude, this study utilized the
long term meteorological data (1980–2022) for temperature and precipitation. Investigations were carried out for 11 mete-
orological stations located in different topographical zones of Jammu, Kashmir and Ladakh region. The non-parametric
Mann–Kendall test was used for significance of trends in precipitation and temperature data on monthly, seasonal, and
annual scales, while Sen’s non-parametric estimator of the slope was used to estimate the magnitude of trend. For TMax,
except Jammu plains (-0.018oC a− 1) all regions experienced increasing trend with annual rate of increase 0.018oC a− 1,
0.032oC a− 1 and 0.051oC a− 1 in Pir Panjal region, Kashmir valley and Ladakh region respectively. For annual TMin, all four
geographical regions and individual stations have observed an increase. Ladakh region observed highest rate of increase
(0.070oC a− 1) which was significant followed by Pir Panjal region (0.048oC a− 1), Kashmir valley (0.013oC a− 1) and the
lowest rate was observed in Jammu Plains (0.006oC a− 1). Precipitation revealed a general decreasing trend with large inter
annual variability. Seasonally, TMin has seen most significant changes across all topographical regions. Our results indicate
that influence of Indian Summer Monsoon (ISM) was more towards the Jammu plains and its impact reduced towards
Pir Panjal and Kashmir valley with increasing influence of Western Disturbances (WDs). Jammu plains received 75.8%
precipitation from ISM while Kashmir valley received 72.4% precipitation from WDs. Shift in climatic variables could
have serious environmental and socio-economic implications which can alter the regional ecological stability

Article, 2024

The Three-River Headwater Region, also known as China's water tower, is highly sensitive to clima... more The Three-River Headwater Region, also known as China's water tower, is highly sensitive to climate change and has experienced profound hydrological alterations in the last few decades. This study assessed the potential impacts of climate change on all the important hydrological components such as precipitation, evapotranspiration, streamflow, snow-melt flow, and soil moisture (SM) content in the region. For this, climate data (i.e., temperature, precipitation, relative humidity, and windspeed) of three Global Climate Models (i.e., CanESM5, MPI-ESM1.2-HR, and NorESM2-MM) was downscaled with the Statistical DownScaling Model (SDSM) and their ensemble was forced into a hydrological model to simulate the hydrological processes for 1981–2100. The screening process, which is central to all downscaling techniques, is very subjective in the SDSM. Therefore, we developed a quantitative screening approach by modifying the method applied by Mahmood and Babel (2013, https://doi.org/10.1007/s00704-012-0765-0) for the selection of a set of logical predictors to cope with multi-collinearity and their ranking. The analyses were performed for the near future period (NFP, 2021–2060) and far future period (FFP, 2061–2100) relative to the baseline period (BLP, 1981–2020). The results showed that the region will be hotter and wetter in the future, with intensive and frequent floods. For example, temperature, precipitation, evapotranspiration, and streamflow will increase by 1.0–1.5 (1–1.9)°C, 9–21 (15–27)%, 6–17 (9–29)%, and 9–46 (22–64)% in the NFP and by 2.0–2.8 (2.7–4.6)°C, 16–40 (43–87)%, 11–31 (24–73)%, and 20–95 (60–198)% in the FFP, respectively, under SSP2-4.5 (SSP5-8.5). Similar projections were explored for other hydrological components. Among all, surface flow showed an unprecedented increase (500%–1,000%) in the FFP. Peak flows will be much higher and will shift forward, and snowmelt will start earlier in the future. The results of the present study can be a good source for understanding the hydrological cycle and be used for the planning and management of water resources of the highly elevated and complex region of the Qinghai Tibetan Plateau.

Article, 2024

The Three-River Source Region (TRSR), China's water tower and an important ecological barrier in ... more The Three-River Source Region (TRSR), China's water tower and an important ecological barrier in China, provides a considerable amount of water to the downstream regions, home to more than 500 million people. The present study focused on the assessment of hydrological components (i.e., precipitation, actual evapotranspiration, potential evapotranspiration, surface flow, baseflow, streamflow, soil moisture, snowmelt water, and terrestrial water storage), their transformation and trends along with meteorological elements (i.e., maximum temperature, minimum temperature, mean temperature, relative humidity, wind speed, and sunshine hours) in the historical and future periods. For this, the hydrological model, HEC-HMS, was applied to simulate hydrological components and Mann-Kendal to explore the trends for 1981–2015. First time, the statistical downscaling model, SDSM, was used to generate climatic data under the shared socio-economic scenario-5 (SSP585) in the region, which was applied to simulate the hydrological cycle. The assessment results showed that precipitation transformed into evapotranspiration and streamflow by 70 % and 30 %, respectively. In the region, streamflow was generated by 78 %, 22 %, and 5.6 % by baseflow, surface flow, and snowmelt. According to trend results, all climatic variables showed statistically significant trends but insignificant in all hydrological components for the historical period, except evapotranspiration. However, all hydroclimatic components were projected to increase in the future, except windspeed. For example, temperature, precipitation, evapotranspiration, streamflow, and direct flow (surface flow) will increase by 1.4 (3.3) °C, 12 (36) %, 8.5 (19) %, 25 (95) %, and 77 (473) % in 2021–2060 (2061–2100) relative to 1981–2020, which shows, the region will be hotter and wetter, with high flooding potential in the future. These results will be helpful for precise water resources planning and management in this extremely sensitive region to climate change.

Global megatrends in population growth and climate change, together with regional conflicts, are ... more Global megatrends in population growth and climate change, together with regional conflicts, are driving an increasing and unequal demand for food and consequently pose a serious threat to food security worldwide. Studies have shown that increasing cropland productivity, rather than expanding cropland area, may be a more viable strategy to promote food security [1]. From an agronomic perspective, irrigation can greatly enhance crop yield and productivity, particularly in arid regions and during dry seasons [2]. Therefore, irrigation is crucial for improving global crop production and ensuring global food security.

Investigating trends in water use efficiency (WUE) and its causality is critical for understandin... more Investigating trends in water use efficiency (WUE) and its causality is critical for understanding ecosystem behaviors. Although WUE has shown nonlinear changes in the last several decades across most global ecosystems, the majority of available studies have focused on its linear trend. This study attempted to accurately attribute the linear and nonlinear variations in WUE using normalized driving factors in the Partial Derivative (PD) equation to develop a Normalized Partial Derivative model (NPD-model). Two linear trends obtained from the Linear Regression (LR) and Non-Parametric (NP) and a nonlinear trend obtained from the Ensemble Empirical Mode Decomposition (EEMD) are employed in the NPD-model for attributing WUE change in China. The individual and relative responses of driving factors to WUE change during 2000–2018 are quantified using the China version of the PML-V2 evapotranspiration and gross primary productivity products. The results show that the nonlinear EEMD-based NPD-model with an R2 of 0.83, performs best compared to the LR- and NP-based NPD-models, which have R2 values of 0.64 and 0.7, respectively. WUE increased monotonically in most areas of all vegetation types, with high variability observed in grassland and shrubland. The EEMD-based attribution analysis indicates that leaf area index is the leading factor in regulating WUE in China, followed by CO2 and climate. The relative contributions revealed that increased WUE in most of China is dominated by the combination of vegetation and environmental factors, covering more than 80% of the study area. These contribution results, however, are largely different from those obtained using the LR- and NP-based NPD-models, as 52% of the study area exhibits cyclic variation in WUE. Therefore, the nonlinear EEMD-based NPD-model provides excellent spatiotemporal attribution of WUE through its driving factors, which is crucial for understanding the ecosystem response to changing environments, potentially assisting in ecosystem and water resource management.

How will climate change affect the sources of global irrigation water withdrawal, 2024

Atmosphere, 2018

In this study, a linear scaling method, precipitation extended linear scaling (PELS), is proposed... more In this study, a linear scaling method, precipitation extended linear scaling (PELS), is proposed to correct precipitation simulated by GCMs. In this method, monthly scaling factors were extended to daily scaling factors (DSFs) to improve the daily variation in precipitation. In addition, DSFs were also checked for outliers and smoothed with a smoothing filter to reduce the effect of noisy DSFs before correcting the GCM's precipitation. This method was evaluated using the observed precipitation of 21 climate stations and five GCMs in the Jhelum River basin, Pakistan and India, for the period of 1986-2000 and also compared with the original linear scaling (OLS) method. The evaluation results showed substantial improvement in the corrected GCM precipitation, especially in case of mean and standard deviation values. Although PELS and OLS showed comparable results, the overall performance of PELS was better than OLS. After Evaluation, PELS was applied to the future precipitation from five GCMs for the period of 2041-2070 under RCP8.5 and RCP2.6 in the Jhelum basin, and the future changes in precipitation were calculated with respect to 1971-2000. According to average all GCMs, annual precipitation was projected to decrease by 4% and 6% in the basin under RCP8.5 and RCP2.6, respectively. Although two seasons, spring and fall, showed some increasing precipitation, the monsoon season showed severe decrease in precipitation, with 22% (RCP8.5) and 29% (RCP2.6), and even more reduction in July and August, up to 34% (RCP8.5) and 36% (RCP2.6). This means if the climate of the world follows the RCP8.5 and RCP2.6, then there will be a severe reduction in precipitation in the Jhelum basin during peak months. It was also observed that decline in precipitation was higher under RCP2.6 than RCP8.5.

Water, 2019

Recent evidence of regional climate change associated with the intensification of human activitie... more Recent evidence of regional climate change associated with the intensification of human activities has led hydrologists to study a flood regime in a non-stationarity context. This study utilized a Bayesian framework with informed priors on shape parameter for a generalized extreme value (GEV) model for the estimation of design flood quantiles for “at site analysis” in a changing environment, and discussed its implications for flood management in the Kabul River basin (KRB), Pakistan. Initially, 29 study sites in the KRB were used to evaluate the annual maximum flood regime by applying the Mann–Kendall test. Stationary (without trend) and a non-stationary (with trend) Bayesian models for flood frequency estimation were used, and their results were compared using the corresponding flood frequency curves (FFCs), along with their uncertainty bounds. The results of trend analysis revealed significant positive trends for 27.6% of the gauges, and 10% showed significant negative trends at t...

Data in Brief, 2019

and Sudan. In the last 40e50 years, the lake has shrunk from a surface area of 25,000 km 2 to 200... more and Sudan. In the last 40e50 years, the lake has shrunk from a surface area of 25,000 km 2 to 2000 km 2. However, the availability and quality of hydro-climatic data for researchers are major barriers to research. Since observed station data is highly sparse in the basin and difficult to collect, monthly climatic data was extracted from the gridded Climate Research Unit (CRU) dataset. The gridded CRU temperature and rainfall data was extracted at 81 points, and monthly temperature and rainfall data was converted into daily data for hydrologic modelling in Mahmood and Jia [1]. This data article also includes observed streamflow data of 3 hydrometric stations and rainfall data of 11 stations, which was obtained from the Lake Chad Basin Commission. Natural streamflow data simulated with hydrologic model at N'Djamena station on the Chari-Logone River is also included in this data article.

Journal of Geographical Sciences, 2016

Water Supply, 2016

The Great Artesian Basin (GAB) in Australia, the largest artesian basin in the world, is rich in ... more The Great Artesian Basin (GAB) in Australia, the largest artesian basin in the world, is rich in groundwater resources. This study analyzed the spatio-temporal characteristics of terrestrial water storage (TWS) in the GAB for 2003–2014 using satellite (Gravity Recovery and Climate Experiment, GRACE) data, hydrological models’ outputs, and in situ data. A slight increase in TWS was observed for the study period. However, there was a rapid increase in TWS in 2010 and 2011 due to two strong La Nina events. Long-term mean monthly TWS changes showed remarkable agreements with net precipitation. Both GRACE derived and in situ groundwater disclosed similar trend patterns. Groundwater estimated from the PCR-GLOBWB model contributes 26.8% (26.4% from GRACE) to the total TWS variation in the entire basin and even more than 50% in the northern regions. Surface water contributes only 3% to the whole basin but more than 60% to Lake Eyre and the Cooper River. Groundwater, especially deeper than 5...

Water, 2016

Pakistan is one of the most highly water-stressed countries in the world and its water resources ... more Pakistan is one of the most highly water-stressed countries in the world and its water resources are greatly vulnerable to changing climatic conditions. The present study investigates the possible impacts of climate change on the water resources of the Kunhar River basin, Pakistan, under A2 and B2 scenarios of HadCM3, a global climate model. After successful development of the hydrological modeling system (HEC-HMS) for the basin, streamflow was simulated for three future

Article, 2024

How will climate change affect the sources of global irrigation water withdrawal, 2024

Atmosphere, 2018

Water, 2019

Data in Brief, 2019

Journal of Geographical Sciences, 2016

Water Supply, 2016

Water, 2016

In the 1960s, Lake Chad was the world’s sixth largest water body, which has since shrunk dramatic... more In the 1960s, Lake Chad was the world’s sixth largest water body, which has since shrunk dramatically from a surface area of 25,000 km2 to only 2,000 km2 in the following 40 years. In the present study, hydro-climatic variability in the Chari-Logone, Komadugu-Yobe, YENG (Yedseram, El-Beid, Ngadda and Gubio basins) as well as Lake Fitri basins and decreasing streamflow to Lake Chad due to climate variability and human activities were separated and quantified using trend analysis, change point analysis, and hydrological approach, for the period of 1951–2015. The results showed very strong signals (α=0.001) of increasing trend in mean temperature, with an average increase of 1.4 °C, and very weak (α=0.1) to strong (α=0.01) decreasing signals in precipitation, with an average decrease of 15%. In case of streamflow to Lake Chad, very strong decreasing trends were observed, showing 67% reduction for the whole period. The north-eastern parts were most affected parts in case of increasing temperature and decreasing precipitation. Decreasing flow due to both climate variability and human activities were ranged from 34% to 45% in different decades, from 1972 to 2013. On the whole, a 66% of total decline in streamflow was observed due to human activities and 34% due to climate variability. Most reduction in streamflow (59%) due to climate variability was explored only during 1982–1991 because a devastating drought was occurred during this period. Since human activities caused most reduction in streamflow to Lake Chad than climate, inflow to the lake can be improved by reducing or properly managing the human activities and using sustainable water resources management.