The runoff variation characteristics of Dongting Lake, China • Dehua Mao* • Chang Feng • Hunan Normal University, China *Corresponding author • Hui Zhou • Hunan Normal University/Hydrology and Water Resources Survey Bureau of Hunan Province, China • Guangwei Hu • Hunan Industry University • Zhengzui Li • Hydrology and Water Resources Survey Bureau of Hunan Province, China • Ruizhi Guo • Hunan Normal University, China Abstract Resumen Mao, D., Feng, C., Zhou, H., Hu, G., Li, Z., & Guo, R. (March- Mao, D., Feng, C., Zhou, H., Hu, G., Li, Z., & Guo, R. (marzo- April, 2017). The runoff variation characteristics of Dongting abril, 2017). Características de la variación de escurrimiento del Lake, China. Water Technology and Sciences (in Spanish), 8(2), lago Dongting, China. Tecnología y Ciencias del Agua, 8(2), 77 77-91. 77-91. The runoff variation characteristics of Dongting Lake Se analizaron las características de la variación de escurrimiento were analyzed by applying the methods of concentration del lago Dongting mediante la aplicación de los métodos de grado degree, concentration period, Mann-Kendall trend test, de concentración, periodo de concentración, análisis de tendencias and variation coefficient. The analysis showed that: 1) The de Mann-Kendall y coeficiente de variación. El análisis mostró runoff concentration period of Dongting Lake occurs mainly que 1) el periodo de concentración de escurrimiento del lago between June and July of each year, with the peak time in Dongting ocurre principalmente entre junio y julio de cada año, late June–early July, and the composite vector directions presentándose el tiempo máximo entre finales de junio y principios in concentration period range from 103.2° to 190.2°; 2) The de julio y las direcciones de los vectores compuestos en el periodo de runoff variation coefficient ranges from 0.194 to 0.761, which concentración van de 103.2° a 190.2°; 2) el coeficiente de variación indicates the instability of runoff. Extreme ratios of inflow del escurrimiento oscila entre 0.194 y 0.761, lo cual indica la and outflow are over 0.6 with an obvious attenuation; 3) The inestabilidad del escurrimiento. Las proporciones extremas del flujo alternating pattern between wet years and dry years showed de entrada y el flujo de salida son superiores a 0.6, con una obvia that the water distribution of the four rivers is relatively atenuación; 3) El patrón alternante entre los años húmedos y los equal, while Ouchikou from three bayous is more violent, años secos mostró que la distribución de agua de los cuatro ríos accounting for 32.79% of wet years and 57.38% of dry years es relativamente igual, mientras que en Ouchikou, de tres canales respectively. The drastic change of annual water allocation is pantanosos, es más violento, representando el 32.79% de los años adverse to rational utilization of water resources. húmedos y el 57.38% de los años secos, respectivamente. El drástico cambio de asignación anual de agua es adverso a la explotación Keywords: Runoff variation characteristics, annual racional de los recursos hídricos. variation, concentration degree and period, interannual variation, trend analysis, Dongting Lake. Palabras clave: características de variación de escurrimiento, variación anual, grado y periodo de concentración, variación interanual, análisis de tendencias, lago Dongting. Received: 09/04/2016 Approved: 22/09/2016 ISSN 0187-8336 • Tecnología y Ciencias del Agua, vol. VIII, núm. 2, marzo-abril de 2017, pp. 77-91 Mao et al., The runoff variation characteristics of Dongting Lake in China 78 T ecnología y Ciencias del Agua, vol. VIII, núm. 2, marzo-abril de 2017, pp. 77-91 and flood possibility is very high, what’s worse, what’s high, very is possibility flood and drought rainfall, inter-annual of unevenness the the risk for regional flood Because disaster. of 65% of annual precipitation, which increases about provides September to April from which even in Dongting Lake Region.The wet season 1). in(figure presented matic diagramare River at Chenglingji. The details of the sche Lake, stored, and then discharges into Yangtze River, etc.). Those flows inject into Dongting several small rivers (Miluo River, Xingqiang River (Songzikou, Ouchikou, and Taipingkou) Li River, Yuan River), three bayous of Yangtze River, Zi River, (Xiang Hunan of rivers big four contains inflow The storage. water flood in role surface area 2 625 km largest freshwater lake in China, which has of Dongting River. Yangtze Lake is the second has a close relationship with middle reaches lies across Hunan and Hubei Province stem and stream of Dongting River, Yangtze Lake and on the south bank of Jingjiang River, Located a in the northeast of Hunan Province Over viewofthestudyarea Temporal distribution of precipitation is un is precipitation of distribution Temporal 2 and plays an important Figure 1.Schematicdiagramof studyarea. Figure - - worse; 2003, 2006 and 2011 were In 21 the sustained century, drought situation is getting 1999 flood years (Zhang, Zhang, & Li, 2009). flood year and 1969, 1973, 1980, 1993, 1995 and occurred 5 times.1998 and 2002 are extreme to period 2005, from1970 droughts the extreme 1968 occurred serious droughts. During time and 1963 1960, in while 2000) Mao, 1998; (Mao, terrible floods occurred in 1954, 1996 and 1998 & Gao, 2000). During last 60 years, the most is up to 1.858 billion in agriculture (Li, Zheng, average direct economic loss caused by flood Region. According to the statistics, the annual the most severe disasters in Dongting Lake Lake Region. Flood and drought disasters are drought would possibly happen in Dongting like weather extreme the years, flood the in even of the relationship between runoff (three bayous (three runoff between relationship the of The main aim of this study is an investigation etc. climate precipitation, evaporation, process, analysis of hydrology and sediment transport tion from scholars. Researchers focus on the around the lake, which has caused great atten and water supply in agriculture and industry security water inhabitants’ threatened shortage drought years in Dongting Lake region. Water - • ISSN 0187-8336 Mao et al., The runoff variation characteristics of Dongting Lake in China | | and four rivers) variation and drought and flood the normal distribution table, If UFk < Ua/2, it disasters based on the hydrological database. indicate that the tendency is not obvious; | If UFk > Ua/2, it indicated that there is a signifi- Data and methodology cant trend change. If the UFk value is positive, the long series shows increasing trend and vice Data versa. Make the inverse time series of x repeated computation according to the above process, at Hydrological database from 1951 to 2011 has the same time make UBk = -UFk (k = n, n-1,…, been used in this study which was collected 1). The two curves of UBk and UFk cross at one from hydrological stations on the following riv- point, and the cross point is mutation point. If ers: Songzikou (Xinjiangkou and Shadaoguan), the mutation point is located between the given Taipingkou (Mituosi), Ouchikou (Kangjiagang confidence level of 95%, it means mutation time and Guanjiangpu), Xiang River (Xiangtan), Zi is significant in statistics. River (Taojiang), Yuan River (Taoyuan), Li River (Shimen), Chenglingji (Qilishan). Monthly data Concentration degree and concentration period series were used to analysis annual characteris- method tics. All these data were obtained from Hunan Hydrology Bureau and Bulletin of the Yangtze The calculation principle of concentration de- River Sediment during 2000 and 2011. gree and concentration period method follows (Liu, Li, & Su, 2007): to add the monthly runoff 79 Methodology value up in terms of the vector sum in a year. The ratio of the modulus of resultant vector and Mann-Kendall trend test method annual runoff is the annual runoff concentration degree (Rd). The annual runoff concentration pe- Mann-Kendall (M-K) trend test method is usu- riod (Rp) is the direction of the resultant vector. ally used for identification the mutation charac- Set a monthly runoff for ri (I = 1, 2, 3,.., 12). teristic of a long time series data (Wang, Zhou, The vector ri is divided into horizontal and & Tang, 2011; Zhang, Chen, & Jiang, 2008). M-K vertical direction vector; horizontal vector θ θ trend test method is widely recognized which rix = ri cos i; vertical vector riy = ri sin i; the vector θ does not require the original data obeying cer- angle of the i monthly runoff is i. Calculation tain probability distribution and require only formula: 1 9 - 7 7 submitted random independence. Set the time 12 12 12 12 . p p = = = = sequence x1, x2, x3,… , xn, mi represent the cumula- Rx rix ri cos i Ry riy ri sin i (2) , 7 i=1 i=1 i=1 i=1 1 tive amount that the i sample x is greater than 0 i 2 e d x (1 ≤ j ≤ i). Defined the statistical magnitude: j l i r b k a 12 - 2 2 12 12 o 12 z dk = mi ()2 k n (1) 2 2 r R = Rx + Ry = ri cos i + ri sin i a i () m i=1 i=1 , 2 . If the original sequence is random and 12 m ú n = , independent, the mean and variance of dk re- W ri (3) I I i=1 I V spectively are, E[dk] = k(k - 1)/4, var[dk] = k(k - 1) . l o v (2k + 5)/72 (2 ≤ k ≤ n). Further standardization of , R a R y u var [dk] Rd = 100% Rp = arctan (4) g dk, defined statistic UFk = (dk - E[dk])/ A l W Rx e d (k = 1, 2, 3,…, n). If k > 10, UF converges to the k s a i c standard normal distribution. Adopt bilateral n e i C trend test, given a certain significant level a R stands for monthly runoff synthetic vec- y a í (a = 0.05).