Semi-arid Continental Climate Research Articles

Development of a robust daily soil temperature estimation in semi-arid continental climate using meteorological predictors based on computational intelligent paradigms.

Changes in soil temperature (ST) play an important role in the main mechanisms within the soil, including biological and chemical activities. For instance, they affect the microbial community composition, the speed at which soil organic matter breaks down and becomes minerals. Moreover, the growth and physiological activity of plants are directly influenced by the ST. Additionally, ST indirectly affects plant growth by influencing the accessibility of nutrients in the soil. Therefore, designing an efficient tool for ST estimating at different depths is useful for soil studies by considering meteorological parameters as input parameters, maximal air temperature, minimal air temperature, maximal air relative humidity, minimal air relative humidity, precipitation, and wind speed. This investigation employed various statistical metrics to evaluate the efficacy of the implemented models. These metrics encompassed the correlation coefficient (r), root mean square error (RMSE), Nash-Sutcliffe (NS) efficiency, and mean absolute error (MAE). Hence, this study presented several artificial intelligence-based models, MLPANN, SVR, RFR, and GPR for building robust predictive tools for daily scale ST estimation at 05, 10, 20, 30, 50, and 100cm soil depths. The suggested models are evaluated at two meteorological stations (i.e., Sulaimani and Dukan) located in Kurdistan region, Iraq. Based on assessment of outcomes of this study, the suggested models exhibited exceptional predictive capabilities and comparison of the results showed that among the proposed frameworks, GPR yielded the best results for 05, 10, 20, and 100cm soil depths, with RMSE values of 1.814°C, 1.652°C, 1.773°C, and 2.891°C, respectively. Also, for 50cm soil depth, MLPANN performed the best with an RMSE of 2.289°C at Sulaimani station using the RMSE during the validation phase. Furthermore, GPR produced the most superior outcomes for 10cm, 30cm, and 50cm soil depths, with RMSE values of 1.753°C, 2.270°C, and 2.631°C, respectively. In addition, for 05cm soil depth, SVR achieved the highest level of performance with an RMSE of 1.950°C at Dukan station. The results obtained in this research confirmed that the suggested models have the potential to be effectively used as daily predictive tools at different stations and various depths.

A Transient Seepage–Thermal Stability Model for Cohesionless Soil Slopes in the Semi-Arid Continental Climate of the Canadian Prairies

Seasonal weather variations have a profound effect on the integrity of cohesionless soil slopes in the Canadian Prairies owing to the prevalent semi-arid continental climate. The primary contribution of this research is the development of a transient and two-dimensional stability model that is fully coupled with hydraulic and thermal flows. The model was used to predict the factor of safety (FS) for two slope geometries (18 m height and 26 m height) subjected to three weather scenarios (mean, extreme wet, and extreme dry) and four ponding combinations on the upstream and downstream sides of the slopes under no-load and train-load conditions. Results indicated that for mean climate conditions, FS trends fluctuate till April, followed by an increase that remains constant up to November and decreases thereafter. Generally, the FS shows subdued fluctuations and higher values for the high slope compared with the low slope. For wet climate conditions, the FS patterns are similar to mean conditions, albeit with reduced durations of stability during summer. For dry climate conditions, FS values are higher than mean conditions and nearly constant for most of the year. For no ponding and downstream ponding, FS > 1 throughout the year. In contrast, FS > 1 only during the summer (with reduced time in wet climate and extended time in dry climate conditions) for upstream ponding and upstream–downstream ponding. For train loading, FS shows subdued fluctuations and lower values than the corresponding no-loading scenarios for both slopes. The effects of climate conditions and ponding scenarios are further reduced for the high slope. These findings are useful for decision making with regard to the initial design and ongoing performance of natural slopes and embankments in the cohesionless soils of the region.

Skład frakcjonalny stożków gruzowych w kontekście zróżnicowanego klimatu peryglacjalnych stoków górskich (na przykładzie Spitsbergenu i środkowej Azji) = Grain-Size Composition on Talus Slopes in the context of disparate climatic conditions of periglacial mountain zones (exemplified by Spitsbergen and Central Asia)

Talus slopes origin is connected both with weathering and transport of the rock grain. The formation of these landforms is an effect of many climatological, morphological and geological factors. The grain size of the surface of the talus slope brings some information about the way of transport and deposition mechanisms. The main aim of the paper is to present different talus slope formation in two mountain locations - in arctic periglacial and semi-arid continental periglacial climate zones. Results from two study sites are presented. The first one was located on Spitsbergen Island, on its SW coast, near Polish Polar Station. The climate is arctic and periglacial, the average annual temperature is -3,2°C, annual precipitation is 494,6 mm. The slope is exposed to the west, rock face and talus slope are built with gneiss, crystalline shales with marbles intrusions. There is permafrost as well as an active layer noted on this study site. The second study site is in the Fann Mountains, part of Pamiro-Alay massive in Tajikistan. The annual temperature is about 1-2°C (meteo stations nearby: 6,6°C Iskanderkul 2204 m.a.s.l., 0,7°C Shahristan Pass 3143 m.a.s.l.), annual precipitation is about 300 mm. Slope is exposed to the south, rock material is a Devonian massive limestone. No permafrost was observed in this area. On both study sites, similar methods were used. Profiles with four measuring points were designated. On these points, 0,5 x 0,5 m square were marked and perpendicular photographs from a 1,5 m distance were made. Grain sizes were analyzed in BaseGRAIN software. In Asian periglacial high-mountain conditions lack of permafrost and low precipitation causes, that there is no factor of water. Domination of gravitational processes is sorting material when the heaviest rock fragments are transported longer and are deposited on lower positions on the slope.

Effect of two water deficit regimes on phenolic composition of 15 recovered grapevine varieties in Castilla-La Mancha region (Spain): A comparison with national and international varieties

As a consequence of the climate change effects, the chemical composition of wine grapes is being altered, particularly the phenolic components. For this reason, the drought effect on the phenolic composition of an extensive group of white and red varieties grown under a semi-arid continental Mediterranean climate (La Mancha, Spain) was studied in the 2021 vintage. The study was based on the comparison of the phenolic compounds of minority varieties, using other widely cultivated varieties as a reference. The results obtained indicated that there are currently little-known varieties that can equal or even improve to other reference varieties in terms of phenolic composition. Such varieties may be a good alternative for maintaining wine quality in present and future climate change scenarios.

Changes in soil C–N–P stoichiometry after 20 years of typical artificial vegetation restoration in semiarid continental climate zones

Vegetation restoration is one of the principal strategies for ecosystem recovery in degraded land of fragile regions, which is an important driving factor for soil fertility and elemental circulation. While the relationship between revegetation and soil C–N–P stoichiometry remains unclear. To evaluate the relationships between vegetation restoration and soil C–N–P stoichiometry, the distribution of soil C, N, and P within 0–30 cm soil depth under five typical artificial restored vegetation types on the Loess Plateau was analyzed and the influencing factors were evaluated. The results showed that soil C, N, and P contents were relatively lower at the study site than the mean values for topsoil in China. Compared with other vegetation types (Populus simonii Carr., Pinus tabuliformis Carr., and Caragana korshinskii Kom.), Medicago Sativa L. and Stipa bungeana Trin. helped improve soil fertility better; the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents within the 0–30 cm soil layer respectively maximized under Stipa bungeana Trin. (3.30 g kg−1), Medicago Sativa L. (0.34 g kg−1), and Medicago Sativa L. (0.41 g kg−1). The values of soil C/N, C/P, and N/P for the five vegetation types were 9.50–11.85, 15.36–21.47, and 1.29–1.90, respectively. The contents of SOC and TN under the five vegetation types were significantly (P < 0.001) affected by soil depth and vegetation type (P < 0.001) and decreased with increasing soil depth. However, the TP content was significantly (P < 0.001) affected by vegetation type and not by soil depth. Considering the better adaptability of native species, native herb vegetation types should be considered first for ecological restoration in semiarid continental climate zones.

Effects of sunlight exclusion on leaf gas exchange, berry composition, and wine flavour profile of Cabernet-Sauvignon from the foot of the north side of Mount Tianshan and a semi-arid continental climate

Canopy shading is a widely used viticultural strategy for mitigating early grape berry ripening caused by global warming. In this study, we covered half of the canopy with a black shade cloth from the pea-size stage to harvest. In the fruit zone, canopy shade treatment (ST) reduced daily average solar radiation by about 74.6 % compared to the untreated control (UC), and significantly reduced daily average temperature. ST leaves were found to have lower net assimilation rates and higher internal CO2 concentration than in UC, which resulted in reduced yield, bunch weight, cane starch and berry total soluble solids. A delayed development stage was found in ST berries which had lower pH and higher titratable acid than UC. ST increased both berry and wine anthocyanin concentration while significantly decreasing flavonol concentration. ST wines had higher concentrations of a number of ester compounds and β-damascenone than UC wines, thus significantly enhancing the floral and fruity aroma of ST wines. Higher C6/C9 and fatty acids concentrations in ST berries may have caused higher ester concentrations in ST wines. The results showed significant effects on metabolites in berries and wines caused by canopy shade.

Whether land greening in different geomorphic units are beneficial to water yield in the Yellow River Basin?

Understanding the impacts of climate and land use/land cover (LULC) changes on water yield has great importance for water resource management and policy development, especially in arid and semi-arid areas. However, it is unclear whether land greening under the human land management is beneficial to the water yield of different geomorphic units under the unique climate models. Here, we used InVEST model to estimate the water yield of the Yellow River Basin (YRB) in 2000, 2010 and 2019 and selected different scenarios to analyse the contribution of LULC changes to water yield. The results showed that the water yield of the YRB increased during the study period. The mean depth of water yield (MDWY) of grassland, cultivated land, shrubland and forest decreased in turn, while the annual MDWY of each type increased. Cultivated land and grassland were the main contribution types of water yield in the YRB accounting for about 84% of the total, and the annual water yield of LULC types covered by vegetation increased except for cultivated land. The annual water yield of the Qinghai Tibet Plateau (region Ⅰ) and the Loess Plateau (region III) in the YRB accounted for more than 80% of the total YRB water yield and showed an interannual increasing trend with part of the Mongolia Plateau (region Ⅱ) in the basin. The contribution of LULC to water yield in the whole YRB was small compared with that of precipitation, but LULC changes resulted in benefits for water yield in recent years, especially in region III that is controlled by a warm-temperate semi-arid continental climate and region I that is controlled by a plateau cold climate. However, in region Ⅱ, which is controlled by a mid-temperate semi-arid continental climate, revegetation further weakened the water yield ecosystem service. The results can provide references for land use management to enhance water yield under the background of global climate change.

Wintering Index and Yield Traits for Early, Mid, and Late Season Strawberry for Colder Climates

ABSTRACT In temperate climatic regions where severe winter conditions persist, the winter hardiness and fruit yield of strawberry cultivars vary greatly in perennial production systems. A 4-year study was carried out to investigate the wintering ability of different June-bearing strawberry cultivars in the cold semi-arid continental climate of Manitoba between 2015 and 2018. The wintering index and yield traits of early, mid, and late season strawberry cultivars were evaluated. Six different cultivars tested in each year. ‘Wendy,’ ‘Kent’, and ‘Cabot’ were common in each year. Mid-season cultivar ‘Kent’ and ‘Mira’ yielded significantly (p< .05) higher with greater wintering index compared to early and late season cultivars within each trial and across 4 years. Low winter temperatures with less snow on grounds establish pronounced effect on early season cultivars wintering index. A significant variation for temperatures was recorded for the months within and between years.

Dual plastic film and straw mulching boosts wheat productivity and soil quality under the El Nino in semiarid Kenya

The extreme climate events such as El Nino seriously threaten crop production and agro-ecological sustainability because of the aggravated environmental stresses worldwide, particularly in sub-Saharan Africa. To address this issue, we investigated the effects of dual plastic film and straw mulching in ridge-furrow (RF) system on wheat productivity, soil carbon and nitrogen stocks in a semiarid area in Kenya from 2015 to 2017. The experimental site represents a typical semiarid continental monsoon climate, and soil type is chromic vertisols. Field experiment with randomized block design consisted of six RF treatments as follows: 1) dual black plastic film and straw mulching (RFbS), 2) dual transparent plastic film and straw mulching (RFtS), 3) sole black plastic film mulching (RFb), 4) sole transparent plastic mulching RF (RFt), 5) sole straw mulching (RFS) and 6) no mulching (CK). The results indicated that seasonal dynamics of rainfall and air temperature fit in with the weather type of El Nino over four growing seasons. RFbS, RFtS, RFb and RFt significantly increased soil water storage (SWS), topsoil temperature, aboveground biomass, grain yield and water use efficiency across four growing seasons (p < 0.05) as compared with CK. Among all the treatments, RFbS and RFtS achieved the greatest SWS, AgB, grain yield and WUE, owing to improved soil hydro-thermal status in both treatments. Critically, RFbS and RFtS significantly improved soil organic carbon and total nitrogen, soil bulk density and the C:N ratio following four growing seasons, comparing with other treatments (p < 0.05). Besides, RFbS and RFtS gave the highest economic returns among all treatments. For the first time, we found that dual plastic film and straw mulching could serve as a sustainable land management to boost wheat productivity and improve soil quality under El Nino in semiarid areas of SSA.

Influence of the harvest date on berry compositions and wine profiles of Vitis vinifera L. cv. ‘Cabernet Sauvignon’ under a semiarid continental climate over two consecutive years

The ripeness of a grape is critical to berry composition and to the resultant wine. For wineries with a single cultivar occupying an extensive area, the total soluble solid of grapes can range from 22°Brix to 28°Brix. Accordingly, the influence of different harvest dates (ripeness) on berry compositions and on the resultant wine profile was investigated for Vitis vinifera L. cv. ‘Cabernet Sauvignon.’ Berry dehydration was observed as berry weight and juice yields decreased. Berry anthocyanins were concentrated and methylated anthocyanin levels fluctuated with increasing delays in harvesting. Hexanal and 2-hexenal levels in must decreased significantly as berries ripened. In the resultant wines, 2,3-butanediol levels increased. Wines harvested earlier were lighter, presented lower color intensity (CI) values and higher yellow% levels, and exhibited richer aroma profiles (compounds). Through a principal component analysis and discriminant analysis, the compounds characterizing each harvest date were identified.

Spatiotemporal variability of water vapor over Turkey from GNSS observations during 2009\u20132017 and predictability of ERA-Interim and ARMA model

The present paper investigates precipitable water vapor (PWV) variations over the lower middle latitude Turkish region from the International GNSS Services (IGS) and Turkish Permanent GNSS Network (TPGN) observations. The diurnal, seasonal, annual, and rainfall time behavior of PWV and their relative deviations are presented covering the period from 2009 to 2017. Additionally, the predictions from Auto Regressive Moving Average (ARMA) model and ERA-Interim reanalysis datasets are analyzed to understand their effectiveness over the region. In the first observation, diurnal profile indicates maximum value of PWV over the ocean climate regions whereas minimum value is noticed over the semi-arid continental climate areas of Turkey. The seasonal maximum value of PWV is observed in June solstice followed by September equinox and the lowest value is seen in December solstice followed March equinox. The studies also cover annual variation, grand-mean of tropospheric PWV and PWV intensity from the TPGN confirming the range of PWV between 0 to 45 mm. The PWV time series during 2009 to 2017 exhibit a strong annual variation at all sites, with distinctive peaks and dips occurring approximately in summer and winter, respectively. The precipitation plots displayed a clear increasing pattern in summer but the values are less in winter. However, the annual relative deviation of PWV lies in the range of − 0.5 to 1.5 units for all stations. The highest grand-mean of PWV is registered in 2010 (~ 22 mm) whereas the lowest value is seen in 2011 (~ 11 mm). The spatial variation of PWV shows that the northern boundary of the Turkey, western part of the country and Northern Cyprus have higher magnitude of PWV while the other part of the country like Central and Eastern Turkey have the lower magnitudes of PWV. PWV analysis during the precipitation period reconfirms that the rainfall pattern is not necessary to follow the PWV time series due to interlinked atmospheric processes. However, we found the PWV predictability of ARMA model is relatively better than the ERA-Interim model. Comprehensive analysis of TPGN data over the region may complement towards a better understanding of the tropospheric dynamics, their effects and the future refinements of atmospheric models over the lower middle latitude Turkish region.

Spatio-temporal analysis of precipitable water vapour over northwest china utilizing MERSI/FY-3A products

ABSTRACTNorthwest China is considered as the arid and semi-arid temperate continental climate, where the precipitation is closely related to precipitable water vapour (PWV) content. In this paper, the Medium-Resolution Spectral Imager (MERSI) water vapour products were first used to study the spatial and temporal characteristics of water vapour over Northwest China, which were developed by the National Satellite Meteorological Center of China from the Chinese second-generation polar orbit Meteorological Satellite Fengyun 3A (FY-3A). In order to utilize the MERSI water vapour products, the MERSI 5 min water vapour product is compared respectively with global positioning system (GPS), Aerosol Robotic Network (AERONET) and Radiosonde water vapour data in situ datasets. The results show that the water vapour values of the MERSI product are a slightly lower than referenced data, and the accuracy of MERSI product compared with GPS water vapour is the most agreeable, with a mean absolute percentage error (MAPE) of 22.83%. The PWV content displays a typical spatial distribution pattern in Northwest China that it is the highest in the southeast, the second for the northwest and the lowest in the south-centre. The water vapour content over each province in a descending order is Shaanxi, Ningxia, west of Inner Mongolia, Xinjiang, Gansu and Qinghai. The seasonal variation of water vapour content over Northwest China appears to be lowest in winter, followed by spring, then for autumn, and highest in summer. The PWV content of each province in Northwest China shows the periodic inner-annual variation, that is, the PWV content is lowest in January, and gradually increases with time till it peaks in July, and then decreases monthly afterwards, which agrees with the quadratic polynomial model by months. The standard deviation of the water vapour content in summer is 0.533–1.027 mm, while that in winter is 0.262–0.527 mm.

Deterioration analysis of building calcarenite stone in the House of Venus in the archaeological site of Volubilis (Morocco)

The House of Venus was one of the most luxurious Roman houses of the archaeological site of Volubilis in Morocco, built during the first century. It is located in a rural area that has a semi-arid continental climate. The house was mainly built of a yellowish-beige calcarenite. Currently, this stone shows many deterioration features. The objective of this research was to identify the main decay patterns of the calcarenite stone and to investigate the causes of its deterioration. After representative sampling, fresh and weathered stones were characterized using X-ray diffraction, ion chromatography and thermogravimetric analysis. Results show that besides exposure to strong climatic variations for many centuries, stone deterioration was aggravated by interventions using incompatible materials. Halite and gypsum were the main salts detected in deteriorated stones. Potential sources of these salts were also characterized by ion chromatography and thermogravimetric analysis. The contents of both salts are high in mortars and low in soils. They originated in an inappropriate choice of raw materials to formulate restoration mortars.

Vegetation coverage change and stability in large open-pit coal mine dumps in China during 1990–2015

Ecosystem reconstruction via vegetation restoration is key to comprehensive renewal of the fragile ecological environment of an open-pit mine dump. To investigate vegetation coverage change and stability after mine dump land reclamation, three dumps in the Antaibao open-pit coal mine, northern Shanxi province, China, were used. This region has a typical temperate arid to semi-arid continental monsoon climate. Vegetation coverage was calculated from 11 Landsat remote images taken 1990–2015. Methods included calculation of the Normalized Difference Vegetation Index (NDVI), decomposition of mixed pixels, calculation of variation trends, and a transition matrix. The results show that vegetation coverage in the dumps increased dramatically from 1990 to 2015 (with NDVI rising from −0.02 to 0.02 in 1990 to 0.24 to 0.31 in 2015). The change in NDVI was classified mainly as significantly improved, to mostly moderately high coverage, by 2015. Water is a restrictive factor that greatly influenced the growth and development of vegetation. There was greater vegetation coverage and rate of improvement in coverage at higher elevations, and less coverage on steep slopes. Stability analysis of vegetation coverage succession and its recovery after a fire indicate that post-reclamation vegetation coverage in the dumps is relatively stable.

Smooth bromegrass seed yield and yield component responses to seeding rates and row spacings in two climates

Successful grass seed production depends on identifying a suitable environment for the species and proper agronomic practices. Previous research on many species has addressed identifying appropriate agronomic practices for grass seed production, but these studies have not evaluated the effects of environment. By conducting the same experiments in Jiuquan, China (a desert climate) and Tongliao, China (a semiarid continental monsoon climate), the effects of environment, seeding rate, row spacing and their interactions were determined for smooth bromegrass (Bromus inermis Leyss) seed production. Three seeding rates (.3, .5, and .7 g m−1 pure live seed) and four row spacings (30, 50, 70, and 90 cm) were evaluated over three years. Jiuquan had comparable seed yield (SY) and greater thousand-seed weight (TSW) than Tongliao. Three-year average SY decreased with increased row spacings at both sites. Results suggest that in both climates, successful smooth bromegrass seed production was possible, but greater TSW is predicted for desert climates with good irrigation conditions than in semiarid continental monsoon climates due to greater sunshine duration (574 h compared with 527 h) and low relative humidity during seed development (48% vs. 66%). A seeding rate of .3 g m−1 and a row spacing of no wider than 30 cm appears to be adequate for smooth bromegrass seed production in these research locations and in similar ecological regions around the world.

Use Of The Thermo-Hygro Buttons in Tracking The Influence Of Humidity And Temperature On The Deterioration Of The Building Stones Of The Mausoleum Of Imedghassen Batna In Algeria

The tomb of Imedghassen is a pre-Roman royal mausoleum located at 420 Km from Algiers. It is dated back to the 3 rd century B.C. It is built with building stones. The semi-arid continental climate, of the chosen location, is characterized by strong temperature fluctuations and high evaporation. These two factors have a great influence on the building stones’ state of degradation. The infiltration of water in this very rainy region, related to time ,had a serious impact on the monument. To get accurate results about the influence of temperature and humidity, we had controlled the microclimate of the mausoleum using PC Thermo track; thermo-hygro buttons. It allowed us to accurately track the values of the average and higher temperature and humidity, and also the dew point. The results clearly show the relationship between these factors and the origin of the building stone deterioration.

Performance Evaluation of Modern Building Thermal Envelope Designs in the Semi-Arid Continental Climate of Tehran

In this paper we evaluate the thermal performance of a range of modern wall constructions used in the residential buildings of Tehran in order to find the most appropriate alternative to the traditional un-fired clay and brick materials, which are increasingly being replaced in favor of more slender wall constructions employing hollow clay, autoclaved aerated concrete or light expanded clay aggregate blocks. The importance of improving the building envelope through estimating the potential for energy saving due to the application of the most energy-efficient wall type is presented and the wall constructions currently erected in Tehran are introduced along with their dynamic and steady-state thermal properties. The application of a dynamic simulation tool is explained and the output of the thermal simulation model is compared with the dynamic thermal properties of the wall constructions to assess their performance in summer and in winter. Finally, the best and worst wall type in terms of their cyclic thermal performance and their ability to moderate outdoor conditions is identified through comparison of the predicted indoor temperature and a target comfort temperature.

Contribution to the Study of the Origin of Salinity in Alluvial Aquifer System in the Ain Chabro-Hammamet (North-East Algeria)

Tebessa is located in the Algerian North East. It is characterized by a semi-arid continental climate with an average interannual precipitation of less than 400 mm. It belongs to the Eastern Saharian Atlas field along the Tunisian borders. It is drained by a certain number of the wouady of which Chabro and Bouakous are the most important. The surface area of the region extends over 420.6 km2. Problem statement: This region has been a very intense drought during the last 20 years (1980/2000). This drought has generally led to: a general lowering of the water table; the draining water from low depth wells; in particular, the unwatering of the pumping equipment, involving a reduction of the flow drillings and the drying-up of the natural springs. Approach: Therefore, the quantitative and qualitative repercussions were shown on groundwater resources in the area. Four sampling of two years (2005, 2006) has been realized during the high and low waters period. The chemical analysis and the piezometric measures have been done to raise up representative quality and the chart piezometric of the current water table state. Results: The hydro-chemical survey of the groundwater quality, as well as its evolution in the time and the space is become very necessary; especially when the water was destined to the supply of drinking water is continuously deteriorating. It was proved that, the salinity was about 4 g L−1, and the electric conductivity was varied between (997-9120 µS cms−1 in the wells and 468-2500 µS cms−1 in drillings). Conclusions: Thus, the results were obtained shows that, the origin of water salinity were associated to the dissolution of geological formations (evaporate and carbonated), as well as the effects of anthropogenic surface pollution.

Outline of the Yellow River basin, China

The paper aims to summarize the features of the Yellow River basin from viewpoints of physiographic conditions, climate, hydrography, economic development and water resources demand. The Yellow River basin is higher in the west and lower in the east, descending in three huge topographic steps. Most of the area belongs to the arid and semiarid continental monsoon climate zones and relatively dry. The main stream of the basin is 5,464 km long, and divided into upper, middle and lower reaches. The catchment area for upper reach is 38.6×10 km, and that for middle reach is the same, but lower reach very small (2.24×10 km). Both the upper and middle reaches are sections of rich water resources, but the middle reaches are also the main source for silt load. Economic development is presently unbalanced between upper-middle and middle-lower reaches. Based on these datasets, water demand for 2010 and 2020 is predicted.

Using farmers' knowledge for defining criteria for land qualities in biophysical land evaluation

AbstractThe objective of this paper is to present a way of complementing empirical results with farmers' perceptions in defining limiting biophysical land properties in a land suitability evaluation using the FAO framework methodology. The farmers' perceptions were identified using rapid and participatory rural appraisal (RRA/PRA) tools. The study catchment, having a semiarid continental climate and located on the Loess Plateau in northern China, covered an area of 3.5 km2. Most of the land users were dependent on subsistence agriculture. There were important topographic variations in the catchment and arable cropping on steep slopes brought about degradation of land due to water erosion. The biophysical monitoring, soil survey and RRA/PRA survey, carried out one year prior to the present investigation, supplied the data needed for identification of preliminary limiting land properties and land evaluation units. The land properties that needed further investigation in the present study were slope aspect, soil workability, flooding hazard and farmers' criteria on choice of land‐use type. The farmers were able to give a comprehensive picture of the spatial and temporal variation and the importance for land‐use options of the land properties concerned, and thereby complement the information gained from empirical results (measurements). In order to guarantee good production for dry as well as wet years, both south‐ and north‐facing sites were chosen for most crops, and the slope aspect did not need to be differentiated in the final land suitability evaluation for arable crops. Grassland, however, was considered to be more suitable than woodland on south‐facing sites. Hard soil layers were found to be important, since they affected soil workability and erosion negatively, giving slightly reduced suitability for the land units in which they occurred. Flooding events affecting crops on alluvial soils negatively were considered to occur once every 5 to 10 years, which is considered to be a low rate, so this property was therefore not included in the final suitability evaluation. Copyright © 2001 John Wiley &amp; Sons, Ltd.