Double Mass Curve Research Articles

Downward Trends in Streamflow and Sediment Yield Associated with Soil and Water Conservation in the Tingjiang River Watershed, Southeast China

Soil erosion is one of the most serious environment problems in China. Soil and water conservation (SWC) measures play an important role in reducing streamflow and sediment yields. A nested watershed approach, together with the Mann–Kendall trend test, double mass curve, and path analysis were used to quantitatively explore hydrological effects of SWC measures in the Tingjiang River Watershed. Results showed the annual streamflow and sediment yields tended toward a remarkable downward trend since the implementation of SWC measures during 1982–2014, indicating that SWC measures produced significant hydrological effects. The contribution of precipitation to annual streamflow increased from 71% to 79% from the periods 1982–2000 to 2000–2014, indicating decreases in annual precipitation after 2003 and stronger impacts on streamflow than that of SWC measures. However, the contribution of SWC measures to sediment yields increased from 11% to 64% from 1982 to 2014 and gradually dominated contributions to the sediment yields in the watershed. An ecological threshold was established at which the proportion of the cumulative afforestation area due to SWC reaches 10% of the whole watershed, and the remarkable improvements of hydrological effects in the watershed can be observed. These findings could be used to evaluate performance of SWC measures in watersheds.

Relationship between sediment load and climate extremes in the major Chinese rivers

Global warming has led to increase in climate extremes, which altered both hydrological cycles and soil erosion processes. However, the responses of river sediment load to climate change, especially climate extremes have not been well understood due to a lack of comprehensive assessment. This study investigated the temporal trends and spatial patterns of sediment load at 70 hydrological stations during the period of 1956–2019 in ten major river basins in China. Both the partial linear square regression model and the double mass curve method were used to quantify the contribution of key climatic indices and anthropogenic driving forces. Overall, the annual total sediment load exhibited a significant negative trend (P < 0.01), decreasing from 1842.18 Mt/yr in 1960 s to 322.72 Mt/yr in 2010 s (82.48 %). The significant decline of sediment load was particularly obvious in the Yangtze River basin and the Yellow River basin. The abrupt changes of sediment load mostly occurred in 1985–2000. Human activities were primarily response for sediment load changes in most basins. The sediment load in mainstream was mainly regulated by reservoirs, while the tributaries were largely affected by soil and water conservation measures. Intensive human activities have led to substantial changes in land surface and resulted in weakened correlation between sediment load and climate extremes. Generally, precipitation, erosive rainfall and precipitation amount in flood period were closely related to sediment load. In the Southwest River basin and Northwest River basin, the sediment load had a relatively good relationship with extreme temperature, which was related to alpine snowmelt and permafrost degradation due to climate warming. This study provides good insights for a better understanding of the interaction between river sediment load and climate extremes variables, which will be valuable for decision-making in river basin management.

Significant regime shifts in historical water yield in the Upper Brahmaputra River basin

Abstract. Although evidence of the hydrological response of watersheds to climate change is abundant, reliable assessments of water yield (WY) over mountainous regions, such as the Upper Brahmaputra River (UBR) basin, remain unclear. Here, we examine long-term WY changes during 1982–2013 in the UBR basin, based on multi-station runoff observations. We find that there are significant shifts in hydrological regimes in the late 1990s; WY increases in the range of ∼10 % to ∼80 %, while the directions reverse from increasing to decreasing. Additionally, the double mass curve (DMC) technique is used to assess the effects of climate, vegetation, and cryosphere on WY changes. Results show that cryosphere and climate together contribute to over 80 % of the increase in WY across the entire UBR basin, while the role of vegetation is negligible. The combined effects, however, are either offsetting or additive, thus leading to slight or substantial magnitude increases, respectively. The downward WY trend has primarily been regulated by decreased precipitation in recent years. However, we find that meltwater may alleviate the resulting water shortage in some basins. Therefore, the combined effects of climate and cryosphere on WY should be considered in future water resources management over mountainous basins, particularly involving co-benefits between upstream and downstream regions.

Insights into runoff changes in the source region of Yellow River under frozen ground degradation

The source region of the Yellow River (SRYR) in the northeastern Tibetan Plateau is critical for supplying water resources to downstream areas. However, streamflow in the SRYR declined despite a slight increase in precipitation during the past few decades. The SRYR experienced significant frozen ground degradation with climate warming, but how frozen ground degradation influences runoff remains unclear. This study investigated the changes of the precipitation-runoff relationship using the double-mass curve method and examined the impact of long-term spatiotemporal changes in frozen ground on the water balance components using the geomorphology-based eco-hydrological model (GBEHM). The results showed that the precipitation-runoff relationship changed significantly since 1989 in the SRYR from 1960 to 2019. In the same period, the areal mean value of the maximum thickness of seasonally frozen ground (MTSFG) decreased by 0.10 m/10a and the areal mean active layer thickness (ALT) of permafrost increased by 0.06 m/10a. Besides, 21.0 % of the entire SRYR has degraded from permafrost to seasonally frozen ground (SFG). Runoff decreased mainly in the region with elevation below 4200 m, where the evapotranspiration increase exceeded the precipitation increase. Frozen ground degradation significantly altered the hydrological processes, which is reflected by the increased subsurface runoff and the decreased surface runoff. The total water storage increased by 2.9 mm/a in the permafrost region due to the increase in active layer thickness and by 5.7 mm/a in the degradation region where permafrost completely thawed during 1960–2019. The runoff seasonality was also altered, being indicated as an increase in winter runoff. These findings help provide a better understanding of the runoff change under climate warming in permafrost-affected regions and provide insights into future water resources management in the Yellow River basin under the climate warming.

Hydrological data and modeling to combine and validate precipitation datasets relevant to hydrological applications

Study RegionForty-one river basins in Brazil and neighboring countries in South America. Study FocusIn large river basins, on countrywide or continental scales, it is often difficult to have consistent and accurate long time series of spatially distributed precipitation data available. However, these are needed to calibrate hydrological models and to run hydrological simulations continuously in real-time streamflow forecasting. In this study, we assess two real-time precipitation products based on rain gauges and satellite data (TRMM-MERGE and CPC-NOAA) for their use in streamflow forecasting in the hydropower sector in Brazil. To take advantage of each precipitation data source and derive a unique dataset, a methodology is proposed to combine, extend, and validate the datasets. We consider the discharges at the river basin outlets as an independent and robust reference for hydrological applications. Observed discharges are used to quantify precipitation uncertainties and to weight the blending, while discharges obtained from hydrological modeling are used to validate the final precipitation product. New Hydrological Insights for the RegionThe proposed blending method, which uses the uncertainty of the original datasets to define the weighting factors, was efficient in generating a precipitation product that performs better than each dataset separately when used to force a hydrological model. The use of the double-mass curve correlation to extend the time series of the datasets beyond their common period allowed us to produce long time series of precipitation for South American basins and hydrological applications. The study shows that it is possible to rely on river discharge data and hydrological modeling to select and combine different precipitation products in the region and presents a step-by-step methodology to do so.

Changes in precipitation and discharge in a Mediterranean catchment as a response to climate change and human activities

AbstractThe Mediterranean region is considered to be highly affected by climate change with rainfall deficits leading to a significant decrease in river discharge. This study aims to assess the impacts of climate change on water resources in a Mediterranean catchment, namely the Bas-Loukkos catchment (Morocco), where pressure on the water resources is already present due to intensive hydro-agricultural development and is likely to increase. Mann–Kendall, Pettitt and Buishand tests were used to analyze trends and detect breakpoints in discharge and precipitation time series over the period 1960–2018. The precipitation–specific discharge relationships has been analysed by the double-mass curve (DMC). The analyses highlighted a decreasing trend in precipitation. A significant breakpoint was detected in early 1970s, with mean annual precipitation decreasing by 16–26% after this period. Discharge decreased by approximately 35% beginning in the late 1970s/early 1980s. The DMC showed different patterns between ‘undisturbed’ sub-catchments and two intensively managed sub-catchments. Wettest Mediterranean catchments are often considered as future water reservoirs to support part of the water needs in arid catchments. This study highlights that such catchments may already be impacted by climate changes, with discharge decreasing, and by water human activities that exert a major pressure on water resources.

Separating anthropogenic and climate contributions to streamflow variations in Rietspruit sub-basin, South Africa

Human activities and climate change continue to alter streamflow in many river basins. In this study, the influence of human activities and climate variability on streamflow changes in the Rietspruit sub-basin (RSB), South Africa, were investigated using precipitation, potential evapotranspiration, and discharge data for the period 1986 to 2018. Trends in the hydrometeorological variables were assessed using the Mann-Kendall test while the change point in the annual streamflow data was identified using the Pettitt test and the double mass curve technique. Results revealed no statistically significant change in annual precipitation, whereas annual streamflow showed a significant increasing trend while potential evapotranspiration showed a decreasing trend. It was identified that the change point occurred around 1999, thereby dividing the streamflow data into the pre-change (1986–1999) period with comparatively low urban cover (8.3%), and the post-change period (2000–2018) with urban land covering 16.6% of the study area. The results demonstrate that from 1986 to 2018, the elasticity of streamflow with respect to precipitation and potential evapotranspiration was 0.26 and −2.01, respectively. This implies that streamflow in the study area is more sensitive to potential evapotranspiration than precipitation. Nonetheless, changes in land use/land cover, particularly the urban settlement which increased by 101% between 1986 and 2018, were more influential than climate variability for the significant increase in streamflow in the RSB. The results provide necessary information for water resource management, land use planning and ecosystem development in the near future. This study emphasizes the necessity of addressing nonlinear and dynamic hydrological processes as a result of human impact and climate associated changes.

Random Forest Model Has the Potential for Runoff Simulation and Attribution

Quantifying the impact of climate change and human activities on runoff changes is beneficial for developing sustainable water-management strategies within the local ecosystem. Machine-learning models were widely used in scientific research; yet, whether it is applicable for quantifying the contribution of climate change and human activities to runoff changes is not well understood. To provide a new pathway, we quantified the contribution of climate change and human activities to runoff changes using a machine-learning method (random forest model) in two semi-humid basins in this study. Results show that the random forest model provides good performances for runoff simulation; the contributions of climate change and human activities to runoff changes from 1982 to 2014 were found between 6–9% and 91–94% in the Zijinguan basin, and 31–44% and 56–69% in the Daomaguan basin, respectively. Furthermore, the model performances were also compared with those of well-known elasticity-based and double-mass curve methods, and the results of these models are approximate in the investigated basins, which implies that the random forest model has the potential for runoff simulation and for quantifying the impact of climate change and human activities on runoff changes. This study provides a new methodology for studying the impact of climate change and human activities on runoff changes, and the limited numbers of parameters make this methodology important for further applications to other basins elsewhere. Nevertheless, the physical interpretation should be made with caution and more comprehensive comparison work must be performed to assess the model’s applicability.

Inverse Trend in Runoff in the Source Regions of the Yangtze and Yellow Rivers under Changing Environments

The source regions of the Yangtze River (SRYZ) and the Yellow River (SRYR) are sensitive areas of global climate change. Hence, determining the variation characteristics of the runoff and the main influencing factors in this region would be of great significance. In this study, different methods were used to quantify the contributions of climate change and other environmental factors to the runoff variation in the two regions, and the similarities and differences in the driving mechanisms of runoff change in the two regions were explored further. First, the change characteristics of precipitation, potential evapotranspiration, and runoff were analyzed through the observational data of the basin. Then, considering the non-linearity and non-stationarity of the runoff series, a heuristic segmentation algorithm method was used to divide the entire study period into natural and impacted periods. Finally, the effects of climate change and other environmental factors on runoff variation in two regions were evaluated comprehensively using three methods, including the improved double mass curve (IDMC), the slope change ratio of cumulative quantity (SCRCQ), and the Budyko-based elasticity (BBE). Results indicated that the annual precipitation and potential evapotranspiration increased during the study period in the two regions. However, the runoff increased in the SRYZ and decreased in the SRYR. The intra-annual distribution of the runoff in the SRYZ was unimodal during the natural period and bimodal in the SRYR. The mutation test indicated that the change points of annual runoff series in the SRYZ and SRYR occurred in 2004 and 1989, respectively. The attribution analysis methods yielded similar results that climate change had the greatest effect on the runoff variation in the SRYZ, with a contribution of 59.6%~104.6%, and precipitation contributed 65.3%~109.6% of the increase in runoff. In contrast, the runoff variation in the SRYR was mainly controlled by other environmental factors such as permafrost degradation, land desertification, and human water consumption, which contributed 83.7%~96.5% of the decrease in the runoff. The results are meaningful for improving the efficiency of water resources utilization in the SRYZ and SRYR.

Impacts of Hurricane Michael on Watershed Hydrology: A Case Study in the Southeastern United States

Hurricanes are one of the most significant threats to coastal plain forest ecosystems and urban communities of the southeastern U.S., but their implications for watershed hydrology are unclear. Hurricanes have the potential to alter water balances, causing extensive flooding, biogeochemical cycle disruption, and water quality degradation, saltwater intrusion, and increased nutrient sedimentation export in coastal watersheds. This case study focused on Hurricane Michael, a recent catastrophic event that impacted the Gulf coast, the Florida panhandle, southwestern Georgia, and southeastern Alabama. Through empirical (Double Mass Curve) and process-based ecohydrological modeling (WaSSI model) on long-term streamflow data, we explored whether vegetation damage caused by this hurricane resulted in an increase in streamflow two years after the extreme event. We found that monthly streamflow from the Chipola River watershed with an area of 2023 km2 did not change (&lt;6%) appreciably during the first two years following the storm, arguably because only a fraction of the gauged watershed lost substantial tree cover. However, spatially explicit hydrological modeling suggested that several sub-watersheds with the highest decreases in the Normalized Difference Vegetation Index (NDVI) significantly increased their monthly streamflow in 2019 by up to 22%. These modeled streamflow anomalies subsided by the second growing season when vegetation recovered. Overall, this study suggests that changes in vegetation cover after Hurricane Michael did not have lasting impacts on the hydrology of this watershed, and the hydrology of coastal watersheds may be more resilient to hurricane disturbances than previously thought.

A COMPARATIVE STUDY OF MISSING RAINFALL DATA ANALYSIS USING THE METHODS OF INVERSED SQUARE DISTANCE AND ARITHMETIC MEAN

In water resources planning and management, it is essential to have reliable rainfall data. In many cases, rainfall data under the guardian national/ local institution are incomplete. Some data are missing, both monthly and annually. The missing data may persist due to neither damage nor human error. This study aims to estimate the missing rainfall data using two methods, i.e., the inverse square distance and the arithmetic mean methods. The study compared the two mentioned methods using root mean square error (RMSE) and mean absolute error (MAE) and to determine the consistency of rainfall data in all stations using double mass curve analysis. This study utilized the rainfall data from Tepus, Semanu, Rongkop, and Tanjungsari Stations in Gunung Kidul Regency, Yogyakarta Province, Indonesia. The model performance was tested by the root mean square error (RMSE) and mean absolute error (MAE). The rainfall data consistency was determined by double mass curve analysis. The results showed that the arithmetic mean method performed better rather than the inverse square distance method. The smallest RMSE and MAE values in the arithmetic method at the four stations have confirmed the statement. The rainfall data consistency analyzed by the double mass curve is consistent in all stations except Tepus Station.

Quantitative contribution of the Grain for Green Program to vegetation greening and its spatiotemporal variation across the Chinese Loess Plateau

AbstractA distinct greening trend is evident in Asia, especially on the Loess Plateau (LP) of China, which is driven by climate change and large‐scale land‐use‐related ecological projects, especially the 'Grain for Green Program' (GFGP). However, the specific contributions of the GFGP to vegetation greening and the variation of this greening on a large spatiotemporal scale are not yet clear. We used long‐time‐series normalized difference vegetation index datasets and climate datasets based on the double mass curve method to quantify the contributions of ecological projects and climate change to the greening trend on the LP. We found that the interannual fluctuation of vegetation change was likely related to the interannual fluctuation of climate, especially precipitation. The increasing trend of vegetation change after 2005 indicated that the GFGP, as a type of external disturbance, began to improve vegetation growth. The GFGP failed initially to make a positive contribution in the first few years because of the drought conditions in 1999 and 2005. The increased precipitation played a critical role in enhancing the output of the GFGP on the LP after 2005. Then, the contribution of the GFGP increased quickly until 2013, after which it remained stable and reached average values of 58.8% ± 19.34% and 31.7% ± 24.3% in the representative areas that conducted the GFGP and in other regions with a lower implementation intensity of the GFGP, respectively. Our results highlight the contribution the GFGP has made to spatiotemporal variation due to the spatial heterogeneity of the projects, their intensity and the effect of forest stand age.

Partial afforestation has uncertain effect on flood frequency and peak discharge at large catchment scales (100–1000 km2), south‐central Chile

AbstractAn extensive programme of commercial afforestation in south‐central Chile provides a unique opportunity to extend the field‐based understanding of forest impact on floods to the large catchment scale (100–1000 km2). Until now, much of that understanding has been limited to small catchments (&lt;10 km2). Data for an approximately 50‐year period are analysed systematically for four catchments (434–1545 km2) with 18%–54% increases in forest cover. For each catchment, the forest impact is quantified by pairing annual maximum flood frequency curves and peak discharge/storm rainfall relationships for the pre‐ and post‐afforestation periods. These periods are themselves defined using land use surveys and cumulative double mass curves for runoff and rainfall. Scaling the frequency curves with a discharge corresponding to mean annual rainfall normalizes for rainfall differences and thus isolates the effect of forest cover. Partial afforestation rates of up to 50%, while markedly affecting annual evapotranspiration and runoff, have less certain effects on peak discharges. Downward shifts in the flood frequency curves occur following afforestation but appear more readily explained by changes in rainfall regime. These changes include a small decline in annual rainfall and a downward shift in some of the frequency curves for the storm rainfall totals corresponding to the annual maximum discharges. Nevertheless, some forest impact cannot be ruled out and the effect of a 100% change in forest cover on flood response remains unknown. The results suggest complexity in large catchment flood response and provide only weak support for afforestation with the sole purpose of reducing flood peaks at the large catchment scale. This is a significant conclusion, given that it challenges the largely uncritical view among the public, governments and development agencies worldwide that forests prevent floods.

Analysis of Rainfall Variability in the Province of Quirino

The temporal variability of rainfall in Quirino Province was analyzed through the use of rainfall data of seven (7) rain gauges within the neighboring provinces like Nueva Vizcaya and Aurora. The length of record analyzed from 1997 to 2016. In this study, rainfall frequency analysis and consistency of rainfall data from the different stations through the use of double mass curve analysis was performed and analyzed. The annual series was used to screen each station’s annual rainfall data while the province’s average Thiessen rainfall was screened using maximum period series process. It was found out that all the data of the seven (7) rainfall stations were consistent. To attain allowable error in estimation of 10%, 5% and 1% for the mean annual rainfall the number of rain gauge station needed in the province should be 18, 72 and 1799, respectively.

Flood and drought analysis of Lingasuru, Raichur District - Karnataka

Raichur district, which falls in the north interior sector of Karnataka has been facing a lot of water management problems starting from severe drought conditions, to contaminated use of groundwater resources. With the incising of more and more aquifers being mapped for Arsenic and other heavy metals contamination, the need for surface water has been increased among the people of Raichur district. The work in this paper is on the Drought prediction and analysis of the area, for planning and execution of water resource development activities. The rainfall data analysis is done by Double mass curve and moving average curve by considering the rainfall data of the past 25 years recorded at respective rain gauge stations. The analysis of drought conditions is done by IMD and SPI methods based on data collected from the rain gauges installed at five different places in our study area. The drought recurrence graph has been plotted and the return period equation is calculated to understand the statistical probability of drought occurrence.

Response of runoff and suspended load to climate change and reservoir construction in the Lancang River

Abstract With the operation of six cascade reservoirs, the flow regime and sediment discharge of the Lancang River have changed greatly. The changes of runoff and suspended load have attracted extensive attention. The hydrological data of Gajiu and Yunjinghong stations in Lancang River from 1964 to 2019 were analyzed by using wavelet analysis, double mass curve and abrupt change analysis. The temporal trends in runoff and suspended load were evaluated. Results revealed that the reduction of suspended load was much more profound than the change of runoff. There was a slight downward trend in annual runoff due to climate change. After the completion of Xiaowan and Nuozhadu reservoirs, the proportion of runoff in flood season decreased by 22.64 and 30.75%, respectively. Wavelet analysis was used to reveal the characteristics of runoff evolution. With the operation of reservoirs, suspended load showed abrupt changes in 1993 and 2008. The amount of suspended load during 2009–2019 decreased by 95.47–98.78% compared with that before the reservoir construction. This paper presents the latest quantitative study on the temporal variation of runoff and suspended load since the completion of Xiaowan and Nuozhadu reservoirs, which is of great importance for guiding the operation of reservoirs and maximizing the value of the whole Lancang-Mekong River basin.

Using four approaches to separate the effects of climate change and human activities on sediment discharge in karst watersheds

Quantifying the relative contributions of climate change and human activities to changes in sediment discharge is closely related to regional water resources, soil management, and healthy ecosystem function. However, few studies have used different methods to decompose influences of climatic variability and human activities on changes to sediment discharge, especially in karst regions of southwest China which are experiencing severe soil erosion. This study systematically reviewed four methods (simple linear regression, double mass curve, sediment identify factor analysis, and elastic coefficient method) to separate the contribution of climate change and human activities to sediment discharge variation in four karst watersheds of southwest China during 1955 to 2015. The trend and abrupt change year of sediment discharge in the four watersheds were obtained using a nonparametric Mann-Kendall trend test and sequential test method, respectively. Result showed that the sediment discharge in all four watersheds all decreased significantly (P < 0.05), and the abrupt change years were 2003 or 2004 for these watersheds. The simple linear regression method, double mass curve method, and elastic coefficient method all indicated that the sediment discharge was mainly influenced by human activities, which contributed more than 73% of the observed change. For the sediment identify factor analysis method, sediment concentration was the principal factor influencing sediment discharge variation. The results provide a reference for evaluating the influence of climate and human activities on sediment discharge, and can aid in preparing regional soil conservation policy in karst watersheds.

Quantitatively distinguishing the factors driving sediment flux variations in the Daling River Basin, North China

Understanding the riverine sediment load regime is crucial to sustainably managing fluvial-deltaic ecosystem restoration. However, in studies on global river sediment transport characteristics, small mountainous rivers (SMRs), transporting 45% of the global sediment flux into the sea, have been largely ignored. Furthermore, SMRs have hydrologic characteristics of instantaneous enormous fluxes under extreme climate, but the research on their driving factors affecting sediment transport is insufficient. Partial derivation method and multiple double mass curves were applied to a small mountainous river in North China, the Daling River to study how the three most variable factors—precipitation, vegetation coverage, and reservoirs—have quantitatively controlled sediment flux in the basin and its subregions in the last 50 years. The results of the two methods showed that the 78.55% reduction in sediment flux from 1961–1979 to 1980–2015 was due primarily to restored vegetation coverage (50.42%-61.11%), followed by reservoirs (18.13–44.09%) and precipitation (5.49–22.34%) in the Daling River Basin (DRB) and its subregions. The restored vegetation in the DRB has intercepted a large amount of sediment, reducing the sediment flux transported to the reservoirs. Besides, the Daling River releases enormous amounts of sediment during heavy rainfalls. However, increasing vegetation coverage in recent years has changed the transport characteristics of sediment into temperate changes in runoff and sediment flux under extreme climatic conditions; thus this river provides a useful example of studying the characteristics of sediment transport controlled by nature and human activities against extreme climate conditions. In the DRB, topography, lithology, and vegetation density are the motivators for the differences in sediment flux and its change rates, from upstream to downstream. These findings emphasize the crucial role of vegetation in driving sediment transport from source to sink in temperate SMRs.

Determining the drivers and rates of soil erosion on the Loess Plateau since 1901

Attributing soil erosion to land management and climatic drivers is important for global policy development to protect soils. The Chinese Loess Plateau is one of the most eroded areas in the world. However, there has been limited assessment of historic spatial changes in erosion rates on the Loess Plateau and the major contributors driving these spatial changes. In this study, the Revised Universal Soil Loss Equation was empirically validated and employed to assess spatially distributed historical erosion rates on the Loess Plateau from 1901 to 2016. A double mass curve attribution technique was then used to investigate the impact of land management and climatic drivers on the Loess Plateau. Decadal average erosion rates and the total area with intensive erosion (>5000 t km−2 yr−1) experienced a sharp increase from the 1930s to 1970s, followed by a decline to an historic low between the 1980s and 2000s. Mean erosion rates for the 2000s were 54.3% less than those of the 1970s. However, a recent increase in erosion rates was observed between 2010 and 2016. Land management change was the dominant driver of historical erosion rate changes before 2010. Extensive deforestation and farming, driven by population increase, were responsible for intensifying erosion between the 1930s and 1970s, while policy-driven conservation schemes and revegetation led to reduction thereafter. However, the recent increase in erosion between 2010 and 2016 was mainly driven by extreme rainfall events, a major concern given climate change projections. Advanced erosion control strategies are therefore required as part of integrated catchment management that both maintain water supplies for human use during dry periods while reducing erosion during storm events.

Suitability of different precipitation data sources for hydrological analysis: a study from Western Ghats, India.

For hydrological analysis, it is essential to have continuous and long-term precipitation data. However, the precipitation data from rain gauge stations are often insufficient and not continuous. At present, ground-based gridded data and satellite-based gridded data are often used as an alternative. However, these data sets have to be evaluated for their suitability in hydrological studies. The current study compared three different rainfall data sources with the observed station data for the Kallada River basin of Kerala, India. The ground-based gridded rainfall data from the India Meteorological Department (IMD), the high-resolution satellite product Tropical Rainfall Measuring Mission (TRMM 3B43, version 7), and the reanalysis data Modern-Era Retrospective Analysis for Research and Applications (MERRA) are used in the analysis. The correlation coefficient, normalized root mean square error, Nash-Sutcliffe efficiency, modified index of agreement, and volumetric efficiency are used as performance indicators. The performance indicator's weights are based on the entropy method. The multi-criteria decision-making techniques like compromise programming and Preference Ranking Organization Method (PROMETHEE II) are used for ranking the precipitation data sources. It is found that IMD ground-based gridded data is ranked 1 among the three data sets. The IMD ground-based gridded data are not homogeneous based on the absolute homogeneity test, even though they had the highest rank. The IMD gridded data are further corrected based on double mass curve analysis. The corrected data were analyzed using the precipitation concentration index (PCI) to assess the temporal variation in precipitation, and it was found that the location falls under a uniform distribution zone.