Fazli Ozturk

M5 model tree application in daily river flow forecasting in Sohu Stream, Turkey

This study investigate the potential of M5 model tree in predicting daily stream flows in Sohu river located within the municipal borders of Ankara, Turkey. The results of the M5 model tree was compared with support vector machines. Both modelling approaches were used to forecast up to 7-day ahead stream flow. A comparison of correlation coefficient and root mean square value indicates that M5 model tree approach works equally well to the SVM for same day discharge prediction. The M5 model tree also works well up to 7-day ahead discharge forecasting in comparison of SVM with this data set. An advantage of using M5 model tree approach is the availability of simple linear models to predict the discharge as well use of less computational time.

Stochastic Modeling of Annual Maximum and Minimum Streamflow of Kelkit Stream

Abstract The aim of this study is to determine whether the daily extreme streamflows could be generated by stochastic models. For the study, a linear stochastic model known as either Box-Jenkins or ARIMA was used. A Mann-Kendal nonparametric test was applied to the daily extreme data sequences to examine the existence of trends. This test showed that there was no trend in the daily data sequences. The ARIMA model is referred as ARMA since there was no trend in the data sequences and thus, the non-seasonal differencing operator is equal to zero. By using the graphs of ACF and PACF, alternative ARMA models were determined. The plots of the ACF show that there was no linear dependence between the daily maximum streamflows, whereas a linear dependence was observed between the daily minimum streamflows. Therefore, modeling of daily maximum data sequences was discarded. There are four ARMA models that fulfilled all the diagnostic checks among selected models from the graphs of ACF and PACF for the daily minimum data sequences. But ARMA (1, 0) with a constant was chosen as the best model by considering Schwarz Bayesian Criterion (SBC). In addition, error estimates were also shown that ARMA (1, 0) with a constant was the best model.

Estimating Pan Evaporation from Limited Meteorological Observations from Turkey

ABSTRACT Pan evaporation measurements are widely used to estimate evapotranspiration and free water evaporation. Pan evaporation measurements are critical to many applications including irrigation system design, irrigation scheduling, and hydrologic modeling. In many locations, reliable climate measurements consist of daily minimum screen temperature, daily maximum, rainfall, and windspeed. In many situations, it is advantageous to calculate rather than measure pan evaporation. Many formulas have been developed which predict pan evaporation as a function of limited meteorological observations. One of them, a simplified version of Penmans evaporation formula, requires only temperature, wind and dewpoint data in addition to latitude and elevation. This paper evaluates the Penpan Equation for the case of a pan and tests its universality. Estimates differ from measured values by about 0.65 mm/day at 19 locations in Turkey.

Yüzey Akış ve Sediment Miktarının AGNPS Modeli ile Belirlenmesi

Bilecik ili Pazaryeri ilcesi Kucukelmali, Gude ve Bahcesultan koyleri arazisi icerisinde bulunan Kurukavak deresi su toplama havzasinda 1994-1996 yillari verileri ile yurutulen arastirmada yuzey akis ve sediment miktari tahmin edilmeye calisilmistir. Bu amacla havzaya ait; topografya, bitki ortusu, toprak, arazi kullanimi ve iklim verileri toplanmis, daha sonra bu veriler cografi bilgi sistemi ortamina aktarilarak AGNPS modeli icin gerekli analizler yapilmistir. Elde edilen harita, tablo ve bireysel verilerle AGNPS modeli yardimiyla yapilan yuzeyakis tahminleri olculen degerlerle karsilastirilmistir. Calisma alanindaki 1994-1996 yillari arasindaki 15 farkli yagis olayindan secilen 8 olaya gore; model degerlerinin gozlem degerleri uzerine etkinligi % 25, belirtme katsayisi 0.43 olarak bulunmustur. Kolmogrov-Smirnov testine gore; P= 0.98, Khikare testi sonucu 2 h= 0.83 olarak bulundugundan gozlem ve model degerlerinin homojen oldugu baska bir deyimle ayni populasyona ait olup model degerlerinin gozlem degerlerini temsil edebilecegi kanisina varilmistir.

Güvenç Havzası Aşındırıcı Güç İndisleri ve Kurak Dönemlerin Belirlenmesi

In this study precipitation, drought and erosivity indices and arid periods of Ankara Yenimahalle Guvenc Basin were determined. Fournier Precipitation Index and Bagnouls-Gaussen Drought Index were calculated using rainfall data that were measured among 1984-2008 in the basin and temperature data that were taken from Turkish State Meteorological Service. Precipitation index was 63.8 and defined as low level, drought index was 112.6 and defined as dry level, erosivity index depending on rainfall and temperature was 5.3 and defined as medium level. Arid periods were determined by using rainfall and temperature data of the basin. The long term drought was occurred in 2002, the short term drought occurred in 1998 and the most severe drought occurred in August in 2008 in the basin.

Ankara’da Ölçülen Yıllık Maksimum Yağışların Bölgesel Frekans Analizi

In this study, regional frequency analysis of precipitation data is carried out through methods of L-moments in Ankara province. Annual maxima precipitation series are formed using daily precipitation records obtained from 32 rainfall gauging station. Firstly, whole stations are assumed one region and then stations are split up three region using cluster analysis due to discordant stations. A set of analysis is carried out through index-flood procedure and regional homogeneity is obtained and suitable probability distribution is selected for each region and probable design precipitation values are estimated for various return periods (T year= 2, 5, 10, 25 and 100) via regional L-moment algorithm. Monte Carlo simulation experiments are applied and regional growth curve components are obtained and absolute bias, bias and root mean square errors (RMSE) of estimated quantiles are computed for assessment of the accuracy of estimated precipitation quantiles.

Debideki değişimin Yeşilırmak Nehri su kalitesi parametrelerine etkisi

In this study, streamflow and water quality variables including specific conductivity (EC), water temperature, Na+, K+, Ca2++Mg2+, CO32-, HCO3-, Cl-, SO42- B, sodium adsorption rate (SAR), hardness and total salt (TS), relationships and hysteresis diagrams were investigated to determine the major processes affecting water quality in the Yesilirmak River. The base-flow water discharge was observed between July and February whereas March April and May represent a peak as a result of seasonal rainfall, snowmelt and run-off. The results indicate that most variables exhibit clockwise hysteresis with high values during the base-flow and lower values during the high discharge. There is a negative relationship between discharge and water quality variables including EC, Na+, K+, Ca2++Mg2+, HCO3-, Cl-, SO42-, SAR, hardness and TS. However, no relationship was obtained between discharge and water temperature, pH, CO32- and B. Among the water quality variables EC, Ca2++Mg2+, HCO3-, SO42-, hardness and TS exhibit an open clockwise loop whereas pH, Na+, K+, Cl- CO32-, SAR and B exhibit a complex loop. Water temperature was the only variable that exhibits counterclockwise loop.