Local Water Cycle Research Articles

Signal of Acceleration and Physical Mechanism of Water Cycle in Xinjiang, China.

Global warming accelerates water cycle with features of regional difference. However, little is known about the physical mechanism behind the phenomenon. To reveal the links between water cycle and climatic environment, we analyzed the changes of water cycle elements and their relationships with climatic and environmental factors. We found that when global warming was significant during the period of 1986-2003, the precipitation in Tarim mountains as well as Xinjiang increased rapidly except for Tarim plains, which indicated that there existed a signal of acceleration for water cycle in Xinjiang. The speed of water cycle is mainly affected by altitude, latitude, longitude, slope direction, and the most fundamental element is temperature. Moreover, according to Clausius-Kela Bai Lung relation, we found that the climate change induced the increase of temperature and accelerated the local water cycle only for the wet places. Our results provide a possible physical mechanisms of water cycle and thus well link the climate change to water circulation.

Weekly variations of discharge and groundwater quality caused by intermittent water supply in an urbanized karst catchment

Summary Leaky sewerage and water distribution networks are an enormous problem throughout the world, specifically in developing countries and regions with water scarcity. Especially in many arid and semi-arid regions, intermittent water supply (IWS) is common practice to cope with water shortage. This study investigates the combined influence of urban activities, IWS and water losses on groundwater quality and discusses the implications for water management. In the city of As-Salt (Jordan), local water supply is mostly based on groundwater from the karst aquifer that underlies the city. Water is delivered to different supply zones for 24, 48 or 60 h each week with drinking water losses of around 50–60%. Fecal contamination in groundwater, mostly originating from the likewise leaky sewer system is a severe challenge for the local water supplier. In order to improve understanding of the local water cycle and contamination dynamics in the aquifer beneath the city, a down gradient spring and an observation well were chosen to identify contaminant occurrence and loads. Nitrate, Escherichia coli , spring discharge and the well water level were monitored for 2 years. Autocorrelation analyses of time series recorded during the dry season revealed weekly periodicity of spring discharge (45 ± 3.9 L s −1 ) and NO 3 -N concentrations (11.4 ± 0.8 mg L −1 ) along with weekly varying E. coli levels partly exceeding 2.420 MPN 100 mL −1 . Cross-correlation analyses demonstrate a significant and inverse correlation of nitrate and discharge variations which points to a periodic dilution of contaminated groundwater by freshwater from the leaking IWS being the principal cause of the observed fluctuations. Contaminant inputs from leaking sewers appear to be rather constant. The results reveal the distinct impact of leaking clean IWS on the local groundwater and subsequently on the local water supply and therefore demonstrate the need for action regarding the mitigation of groundwater contamination and reduction of network losses from sewer leakage. Furthermore, these investigations contribute to an improved understanding of urban water cycle systems in the Middle-East which may help water managers in the region to conserve precious resources.

Using GIS to discover changes in the local water cycle of wetlands – case study Poblockie Peatbog

Abstract The aim of this study is to reconstitute the changes in the local water cycle and plant habitats occurring in wetlands under anthropic influence. The selected area for the study in this paper is the swamp of Pobłockie Peatbog, located in the catchment area of the river Łeba in northern Poland. The fieldwork was performed in October of 2013. Using ArcMap the hydrographic network of the study area in the years 1837, 1918, 1936, 1976 and 2000 were digitized and represented. Using a LIDAR image, the terrain model for the swamp of Pobłockie Peatbog was generated in ArcMap. This was then used to create a map showing the location of runoff pathways from the waterlogged areas. Long-term drainage and the construction of new drainage ditches have led to the encroachment of bog woodland on the originally treeless swamp of Pobłockie Peatbog.

Likely frost events at Gale crater: Analysis from MSL/REMS measurements

We provide indirect evidence for the formation of frost at the surface of Gale crater by analyzing the highest confidence data from simultaneous measurements of relative humidity and ground temperature during the first 1000sols of the Mars Science Laboratory (MSL) mission. We find that except for sol 44, frost events could have occurred only between sols 400 and 710, corresponding to the most humid and coldest time of the year (from early fall to late winter). In particular, measurements at Dingo Gap during sols 529–535, at an unnamed place during sols 554–560, at Kimberley during sols 609–617 and at an unnamed place during sols 673–676 showed the largest likelihood of the occurrence of frost events. At these four locations, the terrain is composed of fine-grained and loosely packed material with thermal inertia values of ∼200 SI units, much lower than the 365±50 SI units value found at the landing ellipse. This is important because terrains with exceptionally low thermal inertia favor the formation of frost by lowering minimum daily ground temperatures. An order-of-magnitude calculation to determine the thickness of the frost layer at these four locations results in values of tenths of µm, while the precipitable water content is a few pr-µm. Therefore, surface frost events can have important implications for the local water cycle at Gale crater. In addition, frost is the most likely type of water that can be temporarily found in bulk amounts on the surface of Mars at low latitudes and therefore can cause weathering, influencing the geology of Gale crater.

An increase in the biogenic aerosol concentration as a contributing factor to the recent wetting trend in Tibetan Plateau.

A significant wetting trend since the early 1980s in Tibetan Plateau (TP) is most conspicuous in central and eastern Asia as shown in the instrumental data and the long-term moisture sensitive tree rings. We found that anomalies in the large-scale oceanic and atmospheric circulations do not play a significant role on the wetting trend in TP. Meanwhile, the weak correlation between local temperature and precipitation suggests that the temperature-induced enhancement of the local water cycle cannot fully explain the wetting trend either. This may indicate the presence of nonlinear processes between local temperature and precipitation. We hypothesize that the current warming may enhance the emissions of the biogenic volatile organic compounds (BVOC) that can increase the secondary organic aerosols (SOA), contributing to the precipitation increase. The wetting trend can increase the vegetation cover and cause a positive feedback on the BVOC emissions. Our simulations indicate a significant contribution of increased BVOC emissions to the regional organic aerosol mass and the simulated increase in BVOC emissions is significantly correlated with the wetting trend in TP.

Life in the treetops: ecophysiological strategies of canopy epiphytes in a tropical montane cloud forest

Tropical montane cloud forests (TMCFs) inhabit regions rich in biodiversity that play an important role in the local and regional water cycle. Canopy plants such as epiphytes and hemiepiphytes are an important component of the biodiversity in the TMCF and therefore play a significant role in the carbon, nutrient, and water cycles. With only partial or no access to resources on the ground, canopy plants may be vulnerable to changes in climate that increase canopy temperatures and decrease atmospheric humidity or precipitation inputs. Despite their importance in the TMCF, little is known about variation in functional strategies relating to drought avoidance or drought tolerance of canopy plants. In this study, we quantified variation in a number of functional traits in 11 species of epiphytes and hemiepiphytes in a Costa Rican TMCF. We also generated pressure–volume and xylem vulnerability curves that we used as indicators of drought tolerance. In addition, we hand‐sectioned fresh leaves and examined cross sections under a microscope to quantify leaf thickness, mesophyll thickness and the thickness of water storage cell layers (i.e., hydrenchyma), if present. Lastly, we determined the capacity for foliar water uptake in the laboratory and measured whole‐plant transpiration in the field.A trade‐off was found between traits that confer relative drought resistance and foliar water uptake capacity vs. traits that confer leaf capacitance and relative drought avoidance. This trade‐off may represent an additional axis of the leaf economics spectrum that is unique to epiphytes. We also found that all species had the capacity for foliar uptake of water and that this process contributed substantially to their water balance. On average, foliar uptake of water contributed to the reabsorption of 70% of the water transpired over a relatively wet, 34‐day study period. Our results indicate that canopy plants can mitigate water loss substantially via internal water storage or that they can directly utilize cloud water to offset losses. Our results indicate that species that rely on foliar uptake of water may be more vulnerable to projected changes in climate than species that buffer the effects of drought via internal water storage.

Integrated modeling of aerosol, cloud, precipitation and land processes at satellite-resolved scales

With support from NASA's Modeling and Analysis Program, we have recently developed the NASA Unified-Weather Research and Forecasting model (NU-WRF). NU-WRF is an observation-driven integrated modeling system that represents aerosol, cloud, precipitation and land processes at satellite-resolved scales. “Satellite-resolved” scales (roughly 1–25 km), bridge the continuum between local (microscale), regional (mesoscale) and global (synoptic) processes. NU-WRF is a superset of the National Center for Atmospheric Research (NCAR) Advanced Research WRF (ARW) dynamical core model, achieved by fully integrating the GSFC Land Information System (LIS, already coupled to WRF), the WRF/Chem enabled version of the GOddard Chemistry Aerosols Radiation Transport (GOCART) model, the Goddard Satellite Data Simulation Unit (G-SDSU), and custom boundary/initial condition preprocessors into a single software release, with source code available by agreement with NASA/GSFC. Full coupling between aerosol, cloud, precipitation and land processes is critical for predicting local and regional water and energy cycles.

Building a field- and model-based climatology of local water and energy cycles in the cultivated Sahel – annual budgets and seasonality

Abstract. In the sub-Saharan Sahel, energy and water cycling at the land surface is pivotal for the regional climate, water resources and land productivity, yet it is still very poorly documented. As a step towards a comprehensive climatological description of surface fluxes in this area, this study provides estimates of long-term average annual budgets and seasonal cycles for two main land use types of the cultivated Sahelian belt: rainfed millet crop and fallow bush. These estimates build on the combination of a 7-year field data set from two typical plots in southwestern Niger with detailed physically based soil–plant–atmosphere modeling, yielding a continuous, comprehensive set of water and energy flux and storage variables over this multiyear period. In the present case in particular, blending field data with mechanistic modeling makes the best use of available data and knowledge for the construction of the multivariate time series. Rather than using the model only to gap-fill observations into a composite series, model–data integration is generalized homogeneously over time by generating the whole series with the entire data-constrained model simulation. Climatological averages of all water and energy variables, with associated sampling uncertainty, are derived at annual to sub-seasonal scales from the time series produced. Similarities and differences in the two ecosystem behaviors are highlighted. Mean annual evapotranspiration is found to represent ~82–85% of rainfall for both systems, but with different soil evaporation/plant transpiration partitioning and different seasonal distribution. The remainder consists entirely of runoff for the fallow, whereas drainage and runoff stand in a 40–60% proportion for the millet field. These results should provide a robust reference for the surface energy- and water-related studies needed in this region. Their significance and the benefits they gain from the innovative data–model integration approach are thoroughly discussed. The model developed in this context has the potential for reliable simulations outside the reported conditions, including changing climate and land cover.

The role of dew in the monsoon season assessed via stable isotopes in an alpine meadow in Northern Tibet

Rain in the summer monsoon season is the main water input for the water cycle in the alpine meadow ecosystem of Northern Tibet, however, dew has been observed frequently in Nagqu, especially during consecutive dry days. Under climate change and human disturbance, degradation of the meadow leads to surface property changes and these may affect dew formation. The amount of dew formed on top of the vegetation surface was therefore measured on normal Kobresia pygmaea meadow and partly-degraded crusted meadow soil for 12 dew days in the 40 observation days from early-July to mid-August in 2011. The converted average daily dew depth was significantly higher on the normal meadow and the average of 0.15mm/night was three times that on the degraded surface between 20:00 and 7:00. To qualitatively identify the role of dew in the local water cycle, water samples from atmospheric water vapour, rain, creek water and groundwater were collected in July and August of 2011 for the analysis of stable water isotopes using the isotope ratio infrared spectroscopy method (IRIS); the vapour samples were collected by cryogenic trapping. It is shown in a δD–δ18O space that the dew contains water that has been terrestrially recycled by evapotranspiration. This research takes an initial step to see the impact of meadow degradation on dew formation, with regard to its formative conditions and moisture source, suggesting that dew may be an active water source for meadow growth and hydrological processes during summer dry spells on the high plateau.

New evidence for the links between the local water cycle and the underground wet sand layer of a mega-dune in the Badain Jaran Desert, China

Scientists and the local government have great concerns about the climate change and water resources in the Badain Jaran Desert of western China. A field study for the local water cycle of a lake-desert system was conducted near the Noertu Lake in the Badain Jaran Desert from 21 June to 26 August 2008. An underground wet sand layer was observed at a depth of 20–50 cm through analysis of datasets collected during the field experiment. Measurements unveiled that the near surface air humidity increased in the nighttime. The sensible and latent heat fluxes were equivalent at a site about 50 m away from the Noertu Lake during the daytime, with mean values of 134.4 and 105.9 W/m2 respectively. The sensible heat flux was dominant at a site about 500 m away from the Noertu Lake, with a mean of 187.7 W/m2, and a mean latent heat flux of only 26.7 W/m2. There were no apparent differences for the land surface energy budget at the two sites during the night time. The latent heat flux was always negative with a mean value of −12.7 W/m2, and the sensible heat flux was either positive or negative with a mean value of 5.10 W/m2. A portion of the local precipitation was evaporated into the air and the top-layer of sand dried quickly after every rainfall event, while another portion seeped deep and was trapped by the underground wet sand layer, and supplied water for surface psammophyte growth. With an increase of air humidity and the occurrence of negative latent heat flux or water vapor condensation around the Noertu Lake during the nighttime, we postulated that the vapor was transported and condensed at the lakeward sand surface, and provided supplemental underground sand pore water. There were links between the local water cycle, underground wet sand layer, psammophyte growth and landscape evolution of the mega-dunes surrounding the lakes in the Badain Jaran Desert of western China.

Towards sustainable sanitation – the HAMBURG WATER Cycle in the settlement Jenfelder Au

One of the largest urban development projects at present in Hamburg is the conversion of former military barracks into a new residential area for about 630 households, called Jenfelder Au. The urban design concept for this 35 ha area follows a high quality approach to develop a carbon-neutral, attractive neighbourhood for approx. 2,000 inhabitants abundant with green space and urban water. HAMBURG WASSER, Hamburg's water supply and wastewater utility, is rethinking the way of wastewater management by implementing an integrated concept for decentralised wastewater treatment and energy production – the so-called HAMBURG WATER Cycle® (HWC) – in this new residential area, based on source control of wastewater. Stormwater, greywater and blackwater are collected separately and then treated separately on site in Jenfelder Au. The realisation of the HWC will be the hitherto largest demonstration of a resource oriented sanitation concept working with vacuum technology for the collection of concentrated blackwater. This concept intends to establish synergy between wastewater management, waste management and energy production, and contributes to an improved local natural water cycle.

Landscape pattern and sustainability of a 1300-year-old agricultural landscape in subtropical mountain areas, Southwestern China

The Hani terrace landscape located in the mountainous areas of Southwestern China has a history of 1300 years and is a classic example of human–environment harmony. This study investigates the spatial distribution and pattern characteristics of land cover in the landscape using geographical information system and remote-sensing techniques. With the synthetic consideration of both physical and cultural factors, the ecological stability of the landscape was discussed. The results showed that ‘terrace’ and ‘forest’ are dominant in the landscape accounting for 43.80% and 44.90% of the total area, respectively. A clear vertical land-cover distribution of ‘higher forest–middle village–lower terrace–lowest river’ can be found on steep slopes. The local climate and its variation with elevation are essential for the stable local water cycle, and the spatial layout of the landscape elements allows for effective material and energy flow within the landscape. Moreover, the obligatory forest and water resource conservation due to the unique history and culture of Hani adds a social layer of protection. The sustainable development of the Hani landscape is expected to provide valuable insights for the present land and environmental management.

Effects of interactive vegetation phenology on the 2003 summer heat waves

This paper investigates the impact of accounting for interactive plant phenology on the simulation of the June and August 2003 European heat waves. A sensitivity analysis is conducted here by using the WRF atmospheric model and the ORCHIDEE land‐surface model over France with (1) a prescribed vegetation corresponding to year 2002 and (2) a dynamical vegetation model that leaves the vegetation freely evolving. It has been found that, accounting for the phenology dynamics has opposite effects on both events, it damps the temperature anomaly in June, while it amplifies the temperature anomaly in August. The evolution of leaf area index in the two simulations reveals the early and fast development of agricultural vegetation in the simulation with freely evolving vegetation. The vegetation also decays earlier in 2003 than during normal years. This behavior has two consequences. In June, the larger foliage development, caused by higher springtime insolation, contributes to enhanced evapotranspiration and therefore land surface cooling which limit the temperature anomaly during the heat wave. This effect is not as visible in mountainous regions where the presence of forest and the absence of agriculture do not lead to the same modulation of the local water cycle. In August, the early leave fall and the critical soil moisture stress contribute to largely suppress evapotranspiration and to enhance sensible heat flux thus amplifying the temperature anomaly. The modulation of the temperature anomaly caused by the effect of interactive vegetation phenology can reach ±1.5°C for an average total anomaly of about 8°C (i.e. ±20%).

Evapotranspiration: A process driving mass transport and energy exchange in the soil‐plant‐atmosphere‐climate system

The role of evapotranspiration (ET) in the global, continental, regional, and local water cycles is reviewed. Elevated atmospheric CO2, air temperature, vapor pressure deficit (D), turbulent transport, radiative transfer, and reduced soil moisture all impact biotic and abiotic processes controlling ET that must be extrapolated to large scales. Suggesting a blueprint to achieve this link is the main compass of this review. Leaf‐scale transpiration (fe) as governed by the plant biochemical demand for CO2 is first considered. When this biochemical demand is combined with mass transfer formulations, the problem remains mathematically intractable, requiring additional assumptions. A mathematical “closure” that assumes stomatal aperture is autonomously regulated so as to maximize the leaf carbon gain while minimizing water loss is proposed, which leads to analytical expressions for leaf‐scale transpiration. This formulation predicts well the effects of elevated atmospheric CO2 and increases in D on fe. The case of soil moisture stress is then considered using extensive gas exchange measurements collected in drought studies. Upscaling the fe to the canopy is then discussed at multiple time scales. The impact of limited soil water availability within the rooting zone on the upscaled ET as well as some plant strategies to cope with prolonged soil moisture stress are briefly presented. Moving further up in direction and scale, the soil‐plant system is then embedded within the atmospheric boundary layer, where the influence of soil moisture on rainfall is outlined. The review concludes by discussing outstanding challenges and how to tackle them by means of novel theoretical, numerical, and experimental approaches.

Accelerated Changes of Environmental Conditions on the Tibetan Plateau Caused by Climate Change

Abstract Variations of land surface parameters over the Tibetan Plateau have great importance on local energy and water cycles, the Asian monsoon, and climate change studies. In this paper, the NOAA/NASA Pathfinder Advanced Very High Resolution Radiometer (AVHRR) Land (PAL) dataset is used to retrieve the land surface temperature (LST), the normalized difference vegetation index (NDVI), and albedo, from 1982 to 2000. Simultaneously, meteorological parameters and land surface heat fluxes are acquired from the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) dataset and the Global Land Data Assimilation System (GLDAS), respectively. Results show that from 1982 to 2000 both the LST and the surface air temperature increased on the Tibetan Plateau (TP). The rate of increase of the LST was 0.26±0.16 K decade−1 and that of the surface air temperature was 0.29 ± 0.16 K decade−1, which exceeded the increase in the Northern Hemisphere (0.054 K decade−1). The plateau-wide annual mean precipitation increased at 2.54 mm decade−1, which indicates that the TP is becoming wetter. The 10-m wind speed decreased at about 0.05±0.03 m s−1 decade−1 from 1982 to 2000, which manifests a steady decline of the Asian monsoon wind. Due to the diminishing ground–air temperature gradient and subdued surface wind speed, the sensible heat flux showed a decline of 3.37 ± 2.19 W m−2 decade−1. The seasonal cycle of land surface parameters could clearly be linked to the patterns of the Asian monsoon. The spatial patterns of sensible heat flux, latent heat flux, and their variance could also be recognized.

A new method for the determination of Holocene palaeohydrology

Summary This paper describes a new method for the assessment of palaeohydrology through the Holocene. A palaeoclimate model was linked with a hydrological model, using a weather generator to correct bias in the rainfall estimates, to simulate the changes in the flood frequency and the groundwater response through the late Pleistocene and Holocene for the Wadi Faynan in southern Jordan, a site considered internationally important due to its rich archaeological heritage spanning the Pleistocene and Holocene. This is the first study to describe the hydrological functioning of the Wadi Faynan, a meso-scale (241 km 2 ) semi-arid catchment, setting this description within the framework of contemporary archaeological investigations. Historic meteorological records were collated and supplemented with new hydrological and water quality data. The modelled outcomes indicate that environmental changes, such as deforestation, had a major impact on the local water cycle and this amplified the effect of the prevailing climate on the flow regime. The results also show that increased rainfall alone does not necessarily imply better conditions for farming and highlight the importance of groundwater. The discussion focuses on the utility of the method and the importance of the local hydrology to the sustained settlement of the Wadi Faynan through pre-history and history.

Using stable isotopes to determine the water sources in alpine ecosystems on the east Qinghai‐Tibet plateau, China

AbstractTo investigate the water circulation of eastern Qinghai‐Tibet plateau during rainy season, water samples of precipitation, throughfall, fog, soil, litter and xylem were collected for stable isotope analysis. The results showed that precipitation mainly originated as a result of the East Asian Monsoon, and the secondarily evaporated water from subalpine ecosystem was an important part in local atmospheric water cycle. The deuterium excess of rainfall in the alpine meadow was evidently higher than the precipitation in the Dengsheng stations. This suggests that a large part of precipitation in alpine meadow was derived from secondarily evaporated water and the mean contribution was 39·57%, about 3·65 mm produced shortly after rain events. Through the contrast of delta (d)‐excess value in different water samples, it could be concluded that the water in subalpine shrubland and transpiration of subalpine dark coniferous forest were the main source of secondarily evaporated water that transferred to alpine meadow. Hence, the precipitation on the east Qinghai‐Tibet plateau was doubly controlled by monsoon and local water circulation in alpine ecosystems. Copyright © 2010 John Wiley & Sons, Ltd.

Simulating observed boundary layer clouds on Mars

A microphysical model for Mars dust and ice clouds has been applied in combination with a model of the planetary boundary layer (PBL) for the interpretation of measurements by the LIDAR instrument on the Phoenix Mars mission. The model simulates nighttime clouds and fall streaks within the PBL that are similar in structure to the LIDAR observations. The observed regular daily pattern of water ice cloud formation and precipitation at the top of the PBL is interpreted as a diurnal process in the local water cycle in which precipitation of large ice crystals (30–50 μm effective radius) results in downward transport of water vapor within the PBL. This is followed by strong vertical mixing during daytime, and this cycle is repeated every sol to confine water vapor within the PBL.

Influence of climatic teleconnections on the temporal isotopic variability as recorded in a firn core from the coastal Dronning Maud Land, East Antarctica

Ice and firn core studies provide one of the most valuable tools for understanding the past climate change. In order to evaluate the temporal isotopic variability recorded in ice and its relevance to environmental changes, stable isotopes of oxygen and hydrogen were studied in a firn core from coastal Dronning Maud Land, East Antarctica. The annual δ18O profile of the core shows a close relation to the El Nino Southern Oscillation (ENSO) variability. The ENSO indices show significant correlation with the surface air temperatures and δ18O values of this region during the austral summer season and support an additional influence related to the Southern Annular Mode (SAM). The correlation between the combined ENSO-SAM index and the summer δ18O record seems to have been caused through an atmospheric mechanism. Snow accumulation in this region illustrates a decreasing trend with opposite relationships with δ18O data and surface air temperature prior and subsequent to the year 1997. A reorganization of the local water cycle is further indicated by the deuterium excess data showing a shift around 1997, consistent with a change in evaporation conditions. The present study thus illustrates the utility of ice-core studies in the reconstruction of past climate change and suggests possible influence of climatic teleconnections on the snow accumulation rates and isotopic profiles of snow in the coastal regions of east Antarctica.

System thinking skills at the elementary school level

AbstractThis study deals with the development of system thinking skills at the elementary school level. It addresses the question of whether elementary school students can deal with complex systems. The sample included 40 4th grade students from one school in a small town in Israel. The students studied an inquiry‐based earth systems curriculum that focuses on the hydro‐cycle. The program involved lab simulations and experiments, direct interaction with components and processes of the water cycle in the outdoor learning environment and knowledge integration activities. Despite the students' minimal initial system thinking abilities, most of them made significant progress with their ability to analyze the hydrological earth system to its components and processes. As a result, they recognized interconnections between components of a system. Some of the students reached higher system thinking abilities, such as identifying interrelationships among several earth systems and identifying hidden parts of the hydrological system. The direct contact with real phenomena and processes in small scale scenarios enabled these students to create a concrete local water cycle, which could later be expanded into large scale abstract global cycles. The incorporation of outdoor inquiry‐based learning with lab inquiry‐based activities and knowledge integration assignments contributed to the 4th grade students' capacity to develop basic system thinking abilities at their young age. This suggests that although system thinking is regarded as a high order thinking skill, it can be developed to a certain extent in elementary school. With a proper long‐term curriculum, these abilities can serve as the basis for the development of higher stages of system thinking at the junior–high/middle school level. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 47: 540–563, 2010