Baseflow Recession Research Articles

Monitoring temporal variations in groundwater levels in urban areas using ground penetrating radar

Monitoring temporal variations in groundwater levels provides a key to sustainable freshwater resource utilization and management, sustainable land use, and sustainable crop acreage, yield, and production. This study used ground penetrating radar (GPR) to monitor temporal variations in groundwater levels in urban areas, and to define the factors that control these variations. The city of Ismailia, Egypt, was selected as a test site because it is experiencing a rise in groundwater levels that poses potential environmental risks, and it lacks the groundwater wells necessary for monitoring and mitigation. Three main GPR profiles were collected in summer (July 2017) and winter (March 2018) using a 100-MHz antenna. On the collected GPR data, water table was defined as a continuous linear reflector of high amplitude. The water table appeared at 8.6 m and 9.5 m (below ground surface) in the summer and the winter surveys, respectively. The depths to the water table, as extracted from GPR surveys, are identical to those measured at a nearby water supply. The higher depth to the water table in the winter is related to excessive groundwater extraction and/or exceptional drought conditions and associated baseflow recession. Results highlight the importance of using GPR in urban areas as a unique, significant, practical, comprehensive, and cost-effective tool to image the subsurface and map the temporal variations in depth to the water table.

Parameter uncertainty with flow variation of the one-dimensional solute transport model for small streams using Markov chain Monte Carlo

The transient storage model (TSM) is a popular solute transport model among hydrologists and ecologists for characterizing solute retention potential of small headwater streams. TSM parameters are most commonly estimated in an inverse modeling framework using tracer breakthrough data. A key challenge in interpreting TSM parameters is the inherent difficulty in the estimation process and relating these parameters with the physical characteristics of streams. While often recognized that multiple sources of uncertainty impact transient storage modeling, rigorous evaluation of TSM parameter uncertainty is rare. Stream flow magnitude has been identified as a key variable in characterizing stream solute transport dynamics, yet no study has shown the impact of flow magnitude on TSM parameter uncertainty. In this paper we study the impact of flow magnitude on TSM parameter uncertainty by using tracer data from repeated tracer studies with changing stream flow magnitudes, and introduce a software tool to perform Markov chain Monte Carlo based parameter estimation and uncertainty evaluation. The software tool developed is capable of performing thousands of model runs within a few hours, which is necessary for Monte Carlo based parameter estimation, and provides a potentially attractive framework for model testing and improvement. TSM parameters were found to be relatively less important during higher flows with large uncertainty bounds and clear evidence of parameter correlations. The importance of TSM parameters on solute transport seemed to increase as flow decreased with seasonal baseflow recession. Our findings highlight the need for improved field methodologies to reduce parameter uncertainty and the need for further improvement in the model structure for successful stream characterization.

Baseflow separation – A practical approach

The satisfactory separation of baseflow from the other components of streamflow has long been a desirable but elusive goal. In the search for consistent and automated baseflow separation techniques, direct applicability to physical processes has been increasingly neglected. By way of contrast, this paper presents a continuous baseflow separation method that emphasises the physical relevance of the flow components, and demonstrates its performance. The proposed method combines the principle of an exponential master baseflow recession with a compatible smoothing function to link the segments of the master recession. Two calibrated parameters facilitate a good fit to a range of streamflow behaviours.

Hydrologic functioning of the deep critical zone and contributions to streamflow in a high‐elevation catchment: Testing of multiple conceptual models

AbstractHigh‐elevation mountain catchments are often subject to large climatic and topographic gradients. Therefore, high‐density hydrogeochemical observations are needed to understand water sources to streamflow and the temporal and spatial behaviour of flow paths. These sources and flow paths vary seasonally, which dictates short‐term storage and the flux of water in the critical zone (CZ) and affect long‐term CZ evolution. This study utilizes multiyear observations of chemical compositions and water residence times from the Santa Catalina Mountains Critical Zone Observatory, Tucson, Arizona to develop and evaluate competing conceptual models of seasonal streamflow generation. These models were tested using endmember mixing analysis, baseflow recession analysis, and tritium model “ages” of various catchment water sources. A conceptual model involving four endmembers (precipitation, soil water, shallow, and deep groundwater) provided the best match to observations. On average, precipitation contributes 39–69% (55 ± 16%), soil water contributes 25–56% (41 ± 16%), shallow groundwater contributes 1–5% (3 ± 2%), and deep groundwater contributes ~0–3% (1 ± 1%) towards annual streamflow. The mixing space comprised two principal planes formed by (a) precipitation‐soil water‐deep groundwater (dry and summer monsoon season samples) and (b) precipitation‐soil water‐shallow groundwater (winter season samples). Groundwater contribution was most important during the wet winter season. During periods of high dynamic groundwater storage and increased hydrologic connectivity (i.e., spring snowmelt), stream water was more geochemically heterogeneous, that is, geochemical heterogeneity of stream water is storage‐dependent. Endmember mixing analysis and 3H model age results indicate that only 1.4 ± 0.3% of the long‐term annual precipitation becomes deep CZ groundwater flux that influences long‐term deep CZ development through both intercatchment and intracatchment deep groundwater flows.

Confirmation of a Short‐Time Expression for the Hydrograph Rising Limb of an Initially Dry Aquifer Using Laboratory Hillslope Outflow Experiments

AbstractThe objective of this study is to assess the validity of a theoretical expression for the outflow from an initially dry aquifer subject to recharge. This equation states that, for small values of time, this outflow is proportional to the square root of time. Here we report on experiments performed with two laboratory hillslopes in the Wageningen rainfall simulator. Three different aquifer slopes were investigated with four replicates for each slope. The relations between the measured outflows and the square root of time exhibited very high coefficients of determination (all but one >0.9). The aquifer saturated hydraulic conductivity (k) and drainable porosity were determined using a base flow recession analysis, with k being consistent with soil physical laboratory measurements. The recharge rates obtained using the coefficient of the short‐time expression and the steady state discharge were consistent as well. Overall, these results confirm the theoretical relationship between the aquifer outflow for the hydrograph rising limb and the square root of time.

Groundwater-flow characterization in a multilayered karst aquifer on the edge of a sedimentary basin in western France

On the edge of sedimentary basins, burial of geological layers can involve the formation of confined karst aquifers. In some cases, relationships between confined and unconfined karst aquifers can exist and imply an increased difficulty in delineating contributive areas of karst system outlets with accuracy. This work aims to develop a multi-disciplinary approach to highlight groundwater exchanges between multilayered karst aquifers feeding a single spring.Toulon Springs, located in western France, provides the opportunity to study relationships between two multilayered karst aquifers. Hydrograph and chemograph analysis coupled with principal component analysis (PCA) are used to evaluate groundwater-flow origins on the northern edge of a sedimentary basin. Natural hydrodynamic responses (baseflow recession analysis, auto-cross correlation function) show an important volume of water located in a saturated zone of the Toulon karst system. Significant contrasts in water quality as a function of the hydrological regime (flood, recession, and baseflow regime) and comparison with shallow and deep water show the participation of a deep aquifer supporting the flow of Toulon Springs.

Applicability Assessment of Estimation Methods for Baseflow Recession Constants in Small Forest Catchments

In South Korea, since small forest catchments are located upstream of most river basins, the baseflow from these catchments is important for a clean water supply to downstream areas. Baseflow recession analysis is widely recognized as a valuable tool for estimating the baseflow component of the stream hydrograph. However, few studies have applied this tool to small forest catchments. So, this study was conducted to assess the applicability of the recession analysis methods proposed in previous studies. The data used were long-term rainfall-runoff data from 1982 to 2011 in the Gwangneung coniferous (GC) and deciduous (GD) forest catchment in Gyeonggi-do, South Korea. For the applicability assessment, six recession constant estimation methods, which were used by previous studies, were selected. The recession constants of the GC and GD catchments were calculated, and applicability assessments were conducted by comparing the recession predictions and baseflow separations. As a result, the recession constants for GC and GD were 0.8480 and 0.9235, respectively. This clear difference may be due to the different forest cover in each area. The correlation regression line, AR(1) model, and the Vogel and Kroll method showed lower error rates and appropriate baseflow indexes compared with other methods.

Climate Elasticity of Low Flows in the Maritime Western U.S. Mountains

AbstractSummer streamflow is an important water resource during the dry summers in the western United States, but the sensitivity of summer minimum streamflow (low flow) to antecedent winter precipitation as compared with summer evaporative demand has not been quantified for the region. We estimate climatic elasticity of low flow (percent change in low flow divided by percent change in climatic forcing variable) with respect to annual maximum snow water equivalent (ESWE), winter precipitation (EPPT), and summer potential evapotranspiration (EPET) for 110 unmanaged headwater catchments in the maritime western U.S. mountains. We find that |EPET| is larger than |EPPT| and |ESWE| in every catchment studied and is 4–5 times larger than both, on average. Spatial variations in E are dominated by three patterns. First, |EPPT|, |ESWE|, and |EPET| are largest and most variable among semiarid catchments and decrease nonlinearly with increasing values of the humidity index (the ratio of annual precipitation to annual evaporative demand). Second, |EPPT| and |EPET| are lower in snow‐dominated catchments than in rain‐dominated catchments, suggesting that snow cover reduces the proportional response of low flows to climatic variability. Third, |EPPT|, |ESWE|, and |EPET| are lower in slow‐draining catchments than in fast‐draining catchments, for which baseflow recession storage coefficients are used to represent the rate at which catchment water storage is translated into streamflow. Our results provide the first comparison of summer low‐flow elasticity to PPT versus PET and its spatial variation in the maritime western U.S. mountains.

ANALISIS KURVA RESESI ALIRAN DASAR MENGGUNAKAN MODEL RESERVOIR LINIER RECESSION CURVE HYDROOFFICE PADA DAS WURYANTORO KABUPATEN WONOGIRI PROPINSI JAWA TENGAH

The hydrograph recession curve expresses the theoretical relationship between the aquifer structure and the flow of groundwater flowing into the river basin channel. These theoretical relationships are often empirically depicted using the base flow recession curve. The hydrograph recession curve is commonly used to estimate the recessionary parameters, aquifer properties and to evaluate alternative hydrological hypotheses. The river basin hydrograph recession curve records the behavior of the relationship between the aquifer structure and its association with groundwater outflow to the river channel. This research was conducted with the aim: to analyze the characteristics of the baseflow recession based on the parameters and coefficients of the recession, and the shape of the individual recession curve and the master recession curve. The characteristics of the baseflow recession to research sub-watershed have the recession curves tend to sloped, describing the water storage well enough. The parameter Q0 (recession early), α and the recession constant Krb ranging from 0,80 – 0,90 for the individual and master recession curve in all three research sub-watershed. This calculation result indicates that the recession characteristics in three research sub-watershed have the condition of water storage is excellent, because they are supported by the aquifer characteristics dominated by the geological structures are more permeable (porous).

Groundwater and surface water connectivity within the recharge area of Guarani aquifer system during El Niño 2014–2016

AbstractRecharge areas of the Guarani Aquifer System (GAS) are particularly sensitive and vulnerable to climate variability; therefore, the understanding of infiltration mechanisms for aquifer recharge and surface run‐off generation represent a relevant issue for water resources management in the southeastern portion of the Brazilian territory, particularly in the Jacaré‐Pepira River watershed. The main purpose of this study is to understand the interactions between precipitation, surface water, and groundwater using stable isotopes during the strong 2014–2016 El Niño Southern Oscillation event. The large variation in the isotopic composition of precipitation (from −9.26‰ to +0.02‰ for δ18O and from −63.3‰ to +17.6‰ for δ2H), mainly associated with regional climatic features, was not reflected in the isotopic composition of surface water (from −7.84‰ to −5.83‰ for δ18O and from −49.7‰ to +33.6‰ for δ2H), mainly due to the monthly sampling frequency, and groundwater (from −7.04‰ to −7.76‰ for δ18O and from −49.5‰ to −44.7‰ for δ2H), which exhibited less variation throughout the year. However, variations in deuterium excess (d‐excess) in groundwater and surface water suggest the occurrence of strong secondary evaporation during the infiltration process, corresponding with groundwater level recovery. Similar isotopic composition in groundwater and surface water, as well as the same temporal variations in d‐excess and line‐conditioned excess denote the strong connectivity between these two reservoirs during baseflow recession periods. Isotopic mass balance modelling and hydrograph separation estimate that the groundwater contribution varied between 70% and 80%, however, during peak flows, the isotopic mass balance tends to overestimate the groundwater contribution when compared with the other hydrograph separation methods. Our findings indicate that the application of isotopic mass balance methods for ungauged rivers draining large groundwater reservoirs, such as the GAS outcrop, could provide a powerful tool for hydrological studies in the future, helping in the identification of flow contributions to river discharge draining these areas.

The impact of urbanization on subsurface flow paths – A paired-catchment isotopic study

Urbanization disturbs groundwater flow through the sealing of native soils with impervious surfaces and through modifications to the subsoil by constructed drainage and other infrastructure (trenches and excavations, e.g. water supply). The impact of these disturbances on groundwater contributions to urban streams (i.e. baseflow) is poorly understood. While high flows caused by impervious runoff to streams are a common focus of urban studies, the route taken by groundwater to become streamflow in urban landscapes is not generally considered. To assess the impact of urbanization on groundwater sources to streams, both rainfall and baseflow were sampled weekly for stable isotopes of water in two nearby streams—one draining a peri-urban catchment and the other draining a forested, natural catchment. In addition, to study the rate of groundwater discharge to the stream, monthly baseflow recession behavior was investigated. We found that baseflow in the forested catchment was constant in stable isotope values (δ18O = −5.73‰ ± 0.14‰) throughout the year. Monthly baseflow recession constants were close to 1 and had little variation (ranging 0.951–0.992), indicating a well-mixed groundwater store and long residence times. In contrast, the urban baseflow isotopic composition featured distinct seasonal variations (δ18O = −3.35‰ ± 1.20‰ from October to March and δ18O = −4.54‰ ± 0.43‰ from April to September) and high week-to-week variability in summer, reflecting a contribution of recent rainfall to baseflow. Recession constants were lower (ranging 0.727–0.955) with pronounced seasonal variations, suggesting shorter residence times and the likely presence of a variety of stores and pathways. These results provide evidence that the urban catchment has diversified groundwater pathways, and its groundwater storage is drained faster than that of the forested catchment. It highlights some of the subsurface hydrological consequences of urbanization. Restoring low-flow aspects of the flow regime through nature-mimicking stormwater management requires careful consideration of how the behavior of natural groundwater pathways can be restored or replicated using innovative stormwater control measures.

Reply to Comment by Roques et al. on “Base Flow Recession from Unsaturated‐Saturated Porous Media considering Lateral Unsaturated Discharge and Aquifer Compressibility”

AbstractRoques et al. (, https://doi.org/10.1002/2017WR022085) claims that they have proposed an exponential time step (ETS) method to improve the computing method of Liang et al. (, https://doi.org/10.1002/2017WR020938) which used a constant time step (CTS) method on the derivative for dQ/dt in field data, where Q is the base flow discharge and t is the time since the start of base flow recession. This reply emphasizes that the main objective of Liang et al. (, https://doi.org/10.1002/2017WR020938) was to develop an analytical model to investigate the effects of the unsaturated flow on base flow recession, not on the data interpretation methods. The analytical model indicates that the base flow recession hydrograph behaves as dQ/dt ∼aQb with the exponent b close to 1 at late times, which is consistent with previous theoretical models. The model of Liang et al. (, https://doi.org/10.1002/2017WR020938) was applied to field data where the derivative of dQ/dt was computed using the CTS method, a method that has been widely adopted in previous studies. The ETS method proposed by Roques et al. (, https://doi.org/10.1016/j.advwatres.2017.07.013) appears to be a good alternative but its accuracy needs further validation. Using slopes to fit field data as proposed by Roques et al. (, https://doi.org/10.1002/2017WR022085) appears to match data satisfactorily at early times whereas it performs less satisfactorily at late times and leads to the exponent b being obviously larger than 1.

Comment on “Base Flow Recession from Unsaturated‐Saturated Porous Media considering Lateral Unsaturated Discharge and Aquifer Compressibility” by Liang, X., H. Zhan, Y.‐K. Zhang, and K. Schilling (2017)

AbstractLiang et al. () presented an analysis of the impacts of unsaturated zone processes on streamflow recession using methodology from Brutsaert and Nieber () with a constant time step in computation of the time derivative of flow. Over the past 10 years, many authors have demonstrated that this method may produce artifacts that lead to incorrect interpretations. To demonstrate the impact of the choice of analysis methods, this comment presents an estimation of recession parameters using the Liang et al. () discharge data that eliminates artifacts introduced through the constant time step. Here we use the exponential time step method, which revealed recession coefficient b greater than 1 which is inconsistent with the fitting framework used in Liang et al. ().

Assessment of Baseflow Estimates Considering Recession Characteristics in SWAT

Baseflow is influenced by incoming groundwater to aquifers and is closely related to watershed characteristics. Understanding baseflow characteristics is of great importance to river ecosystems and water management. Baseflow estimation typically depends on the observed streamflow in gauged watersheds, but accurate predictions of streamflow through modeling can also be useful in estimating baseflow. However, uncertainty occurs in the baseflow estimation process when modeling streamflow. Therefore, the purpose of this study is to compare the method that is proposed by Arnold and Allen (Scenario I) to an improved recession prediction method where the alpha factor (baseflow recession coefficient) is recalibrated and is applied to SWAT (Scenario II). Although the differences between the results (NSE, R2, RMSE, MAE, d) of Scenarios I and II were small regarding streamflow and recession, the Scenario II method more accurately reflected the recession characteristics than the Scenario I method. Furthermore, the Scenario II method was better in baseflow prediction than for the Scenario I method proposed by Arnold and Allen. Therefore, these outputs pave the way and contribute to an efficient method for water management in watersheds.

Separating Wet and Dry Years to Improve Calibration of SWAT in Barrett Watershed, Southern California

Hydrological models often perform poorly in simulating dry years in regions with large inter-annual variability in rainfall. We calibrated the Soil and Water Assessment Tool (SWAT) model to dry and wet years separately, using the semi-arid Barrett watershed on the west coast of USA as an example. We used hydrological and meteorological data from 1980–2010 to calibrate the SWAT model parameters, compared the monthly runoff results simulated by SWAT using a traditional calibration for the entire runoff series with results using a calibration with the wet and dry year series, and analyzed differences in the most sensitive parameters between the wet and dry year series. The results showed that (1) the SWAT model calibrated to the entire runoff series produced significant differences in simulation efficiency between the wet years and dry years, with lower efficiency during the dry years; (2) the calibration with separate wet and dry years greatly enhanced the SWAT model’s simulation efficiency for both wet and dry years; (3) differences in hydrological conditions between wet and dry years were represented by changes in the values of the six most sensitive parameters, including baseflow recession rates, channel infiltration rates, Soil Conservation Service (SCS) curve number, soil evaporation, shallow aquifer flow, and soil water holding capacity. Future work can attempt to determine the physical processes that underlie these parameter changes and their impact on the hydrological response of the semi-arid watersheds.

Spatiotemporal Responses of Groundwater Flow and Aquifer‐River Exchanges to Flood Events

AbstractRapidly rising river stages induced by flood events lead to considerable river water infiltration into aquifers and carry surface‐borne solutes into hyporheic zones which are widely recognized as an important place for the biogeochemical activity. Existing studies for surface‐groundwater exchanges induced by flood events usually limit to a river‐aquifer cross section that is perpendicular to river channels, and neglect groundwater flow in parallel with river channels. In this study, surface‐groundwater exchanges to a flood event are investigated with specific considerations of unconfined flow in direction that is in parallel with river channels. The groundwater flow is described by a two‐dimensional Boussinesq equation and the flood event is described by a diffusive‐type flood wave. Analytical solutions are derived and tested using the numerical solution. The results indicate that river water infiltrates into aquifers quickly during flood events, and mostly returns to the river within a short period of time after the flood event. However, the rest river water will stay in aquifers for a long period of time. The residual river water not only flows back to rivers but also flows to downstream aquifers. The one‐dimensional model of neglecting flow in the direction parallel with river channels will overestimate heads and discharge in upstream aquifers. The return flow induced by the flood event has a power law form with time and has a significant impact on the base flow recession at early times. The solution can match the observed hydraulic heads in riparian zone wells of Iowa during flood events.

Quantifying Modern Recharge and Depletion Rates of the Nubian Aquifer in Egypt

Egypt is currently seeking additional freshwater resources to support national reclamation projects based mainly on the Nubian aquifer groundwater resources. In this study, temporal (April 2002 to June 2016) Gravity Recovery and Climate Experiment (GRACE)-derived terrestrial water storage (TWSGRACE) along with other relevant datasets was used to monitor and quantify modern recharge and depletion rates of the Nubian aquifer in Egypt (NAE) and investigate the interaction of the NAE with artificial lakes. Results indicate: (1) the NAE is receiving a total recharge of 20.27 ± 1.95 km3 during 4/2002−2/2006 and 4/2008–6/2016 periods, (2) recharge events occur only under excessive precipitation conditions over the Nubian recharge domains and/or under a significant rise in Lake Nasser levels, (3) the NAE is witnessing a groundwater depletion of − 13.45 ± 0.82 km3/year during 3/2006–3/2008 period, (4) the observed groundwater depletion is largely related to exceptional drought conditions and/or normal baseflow recession, and (5) a conjunctive surface water and groundwater management plan needs to be adapted to develop sustainable water resources management in the NAE. Findings demonstrate the use of global monthly TWSGRACE solutions as a practical, informative, and cost-effective approach for monitoring aquifer systems across the globe.

A comparison of methods for low streamflow estimation from spot measurements

AbstractLow streamflow statistic estimators at ungauged river sites generally have large errors and uncertainties. This can be due to many reasons, including lack of data, complex hydrologic processes, and the inadequate or improper characterization of watershed hydrogeology. One potential solution is to take a small number of streamflow measurements at an ungauged site to either estimate hydrogeologic indices or transfer information from a nearby site using concurrent streamflow measurements. An analysis of four low streamflow estimation techniques, regional regression, regional plus hydrogeologic indices, baseflow correlation, and scaling, was performed within the Apalachicola–Chattahoochee–Flint watershed, a U.S. Geological Survey WaterSMART region in the south‐eastern United States. The latter three methods employ a nominal number of spot measurements at the ungauged site to improve low streamflow estimation. Results indicate that baseflow correlation and scaling methods, which transfer information from a donor site, can produce improved low streamflow estimators when spot measurements are available. Estimation of hydrogeologic indices from spot measurements improves regional regression models, with the baseflow recession constant having more explanatory power than the aquifer time constant, but these models are generally outperformed by baseflow correlation and scaling.

Characterization and hydraulic behaviour of the complex karst of the Kaibab Plateau and Grand Canyon National Park, USA

Abstract The Kaibab Plateau and Grand Canyon National Park in the USA contain both shallow and deep karst systems, which interact in ways that are not well known, although recent studies have allowed better interpretations of this unique system. Detailed characterization of sinkholes and their distribution on the surface using geographical information system and LiDAR data can be used to relate the infiltration points to the overall hydrogeological system. Flow paths through the deep regional geological structure were delineated using non-toxic fluorescent dyes. The flow characteristics of the coupled aquifer system were evaluated using hydrograph recession curve analysis via discharge data from Roaring Springs, the sole source of the water supply for the Grand Canyon National Park. The interactions between these coupled surface and deep karst systems are complex and challenging to understand. Although the surface karst behaves in much the same way as karst in other similar regions, the deep karst has a base flow recession coefficient an order of magnitude lower than many other karst aquifers throughout the world. Dye trace analysis reveals rapid, conduit-dominated flow that demonstrates fracture connectivity along faults between the surface and deep karst. An understanding of this coupled karst system will better inform aquifer management and research in other complex karst systems.

Identification of the Factors Influencing the Baseflow in the Permafrost Region of the Northeastern Qinghai-Tibet Plateau

Baseflow is an essential component of river runoff. Accurate measurements and analyses of baseflow change are challenging in permafrost-covered regions. In this paper, the upper reaches of the Shule River were selected as the study area, in which to study the baseflow change regulation and causes. The variable infiltration capacity (VIC) model, based on the ARNO baseflow formulation, was used to simulate the baseflow. Simulated baseflow was validated by the isotopic baseflow separation results and measured runoff in the recession periods throughout an entire year. It was found that approximately 63.1% of the river runoff was sourced by baseflow in the study region; the baseflow change was relatively smooth throughout the year, and it lagged a few days behind the river runoff. Approximately 80% of the total baseflow was generated in the 3500–4500 m alpine regions, with mainly low-temperature and mid-temperature permafrost. Based on the climate, runoff, land use, soil temperature and moisture data of the permafrost active layer, the mechanism of baseflow change in the permafrost zone was analysed. Precipitation and temperature positively enhanced the baseflow in the permafrost region throughout a year, but the baseflow was more influenced by the temperature than precipitation. In the study area, the cold desert and alpine grassland had the largest regulation capacity for baseflow. Affected by the permafrost freeze-thaw process, a baseflow peak occurred in the spring and the baseflow recession slowed in the autumn. This lead to a more uniform distribution of baseflow and runoff throughout the year.