| As the bottleneck factors of land use for regional agricultural, the quantity of water resource owns the significant effects whether the land use structure was reasonable. The unreasonable utilization of water resources resulted in a set of unsustainable land resource problems that places a serious constraint on the future of food security, economic development and social stability in dry areas. Naoli River Basin, as the watershed which was cultivated earliest in Sanjiang Plain that located in the Northeastern of Heilongjiang Province, it was one of the most important reclamation area since the establishment of since the founding of new china. Since early 1990 s, the agricultural structure of Naoli River Basin has been greatly adjusted with large amount of dry land which could be easily waterlogged changed into paddy field, water shortages have steadily worsened during the past decade, led the agricultural irrigation water increased sharply, which brought the continued decline of groundwater table, and a series of ecological environment problems caused by secondary. The key point was how to coordinate the distribution of agricultural production, the ecological environment protection in the rational use of local distribution conditions of water resources, which has become serious problems that need to be solved urgently. It should then start to design everything it does around the use of water resources and land resources, intensity of the resources and the coupling relationship between them, which would contribute to the effective protection for the local sustainable utilization of land resources and ecological environment.This study on the farmland change induced land and water resource balance was a basic work on regional sustainable utilization of cultivated land. To reveal the water profit and loss situation of the cultivated land resources in this river basin, this article analyzed the dynamic changes between the dry land and paddy field since 1990 s, and calculated the farmland water requirements of the cultivated land in this basin by modeling the rice planting proportion coefficient which could show the structure of cultivated land, and using the contribution rate that was borrowed from the thought of economics, combing the results of established various types of crop, which was from the research of other scholars, struggled to marry the rate of paddy field and dry land proportion,. All the above analysis used the remote sensing image data, the long-term sequenced meteorological data and the DEM data as its fundamental data resources. By combining the planar climatic elements data which was attained from the dot data interpolation processing for the case of convenient to create the computational condition of reference evapotranspiration(ET0) through using the Penman-Monteith Model, that was generally agreed upon the academic circles, analyzed the condition of Naoli River basin for using the related model to computing the actual evapotranspiration(ET), and by using the established water profit and loss degree evaluation model, structured the order of evaluation standard to analysis the variation of area changes at different levels of moisture shortage, this article discussed the balance effect questions between the soil and water resources under the situation where the cultivated land constantly changed in the basin between 1990 and 2013, and the future land use structure was forecast by using CA-Markov model to reveal the cultivated land scenario simulation, and then discussed the balance effect questions between the soil and water resources under the situation where the cultivated land constantly changed in the future. These research results can be used as references and consultancies for the farmland irrigation schemes in the Naoli River Basin. Results showed as below:(1) Since 1990 a, the large-scale agricultural development activities led to dramatic changes on land using in Naoli River Basin. The area ratio of the dry land, the paddy field and woodland added up to 88%, by 2013, the ratio of paddy field rose to 24.38%, the dry land changed into 43.12%, the woodland decreased to 27.99%, and the unused land had dropped 7.22 percentage points, for its ratio was 1.30%. In 1990 a, the ratio for the construction land was 1.83%, and in 2013, the percentage points rose to 2.13, the water land remained largely unchanged, and the grassland area changed into 0.09×102 km2.(2) The results showed that the land use structure change was mainly dominated by internal and external conversion of cropland. The land conversion area ratio for the sub conversion types of land use in Naoli River Basin of dry land to paddy field, the unused land to dry land, the woodland to dry land and the paddy field to dry land added up to 86.48%; The comprehensive land use change degree in the river basin was 0.70%, and the single land use change degree was between-0.04% to 7.52%, and the paddy field changing phenomenon was the main land use types on the landscape perspective; In Naoli River Basin, the comprehensive index of land use types maintained the overall upward trend obviously for at least 20 years now, and its changing ratio was 7.56%, the change degree which was 251.46 in 1990 rose to 270.48 in 2013, the land utilization degree was increasing continuously in this river basin.(3) In Naoli River Basin, the temporal and spatial distribution of dry land and paddy fields changed fiercely, for the area of paddy fields rose up to 34.00×102 km2,in 2013, the dry land fell slightly to 94.90×102 km2; The area for dry land translated into paddy field was 34.66×102 km2, and its contribution on the conversion rate was 84.60%, followed by unused land, its contribution rate was 13.76%; The conversion types for cultivated land was mainly dominated by internal conversion, and there was about 6.95×102 km2 paddy fields conversion to dry land, and on the way for the dry land out, the area for the sub conversion types to paddy fields was 95.51%; The sub conversion types of dry land to paddy fields mainly occurred in the northern area belong to the Naoli River Basin, Neiqixing River Basin and Waiqixing River Basin and also the eastern area belong the main stream of the central in Naoli River Basin, and this sub conversion types changed violently, paddy fields to dry land was mainly distributed in the southern area scatterly.(4) The farmland water requirements also increased from 541 mm in 1990 to 581.82 mm in 2013. The farmland water requirements keeps rising trend in this period of dry land to paddy field, or more specifically, its water requirements were rising from 541 mm in 1990 to 581.82 mm, and this change mainly concentrated in the northwest and central basin; The spatial pattern of reference evapotranspiration shows increasing characteristic from the northeastern to the southwestern in the river basin of irregular shape; The annual actual evapotranspiration interval was 438~587 mm, These changes were mainly concentrated in the northwest and middle regions of this river basin and the range of the annual actual evapotranspiration was between 438~587mm, its overall distribution characteristic manifested itself as “middle low, two ends high”.(5) The changes of the cultivated land’s water profit and loss degree from 1990 to 2013 in Naoli River Basin were obvious and the spatial distribution differences of the profit and loss index evaluation grades were great. Except for the slight increase of the cultivated land with serious water shortage, the area of the rest four evaluation grades cultivated land all changed strongly. Among them, the area proportion of cultivated land with normal water shortage decreased 22.06%, and the area proportions of the rest three evaluation grades cultivated land all increased 4.74%, 9.61% and 7.72% successively. The above statement shows that the water deficit of the cultivated land in this river basin has been further intensified.(6) The simulation result by the CA-Markov indicated that the Kappa index was 0.82, and it presented reliable prediction results; woodland was the biggest revisions between the land use types, and the paddy field area still maintained growth during this period, but the speed limit had fallen. The dry land area remained constant during 2013 to 2025 years, through the model, the land use degree index would always rise in the future, this reflects that the human and social factors would lead to the intensity of land disturbance during the period of 2013 to 2025 years.(7) Farmland moisture deficit degree would further aggravate in 2025 in Naoli River Basin. The normal moisture shortage and mild moisture shortage types were also the main cultivated land types, but the area of serious moisture shortage types increase obviously, the higher MPLD index would show the distribution characteristic of more focused, and the regional high moisture shortage area could be worse than the last. If no effective measures of protection and control the layout of the land were taken, in the next ten years, the farmland water resources shortage could be more serious in Naoli River Basin.This study provides a scientific basis and decision support for the sustainable development of river basin for the agricultural economy, and also can be used as references and consultancies for the farmland irrigation schemes in the Naoli River Basin. |
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